Merge branch 'js/am-3-merge-recursive-direct'

"git am -3" calls "git merge-recursive" when it needs to fall back
to a three-way merge; this call has been turned into an internal
subroutine call instead of spawning a separate subprocess.

* js/am-3-merge-recursive-direct:
  merge-recursive: flush output buffer even when erroring out
  merge_trees(): ensure that the callers release output buffer
  merge-recursive: offer an option to retain the output in 'obuf'
  merge-recursive: write the commit title in one go
  merge-recursive: flush output buffer before printing error messages
  am -3: use merge_recursive() directly again
  merge-recursive: switch to returning errors instead of dying
  merge-recursive: handle return values indicating errors
  merge-recursive: allow write_tree_from_memory() to error out
  merge-recursive: avoid returning a wholesale struct
  merge_recursive: abort properly upon errors
  prepare the builtins for a libified merge_recursive()
  merge-recursive: clarify code in was_tracked()
  die(_("BUG")): avoid translating bug messages
  die("bug"): report bugs consistently
  t5520: verify that `pull --rebase` shows the helpful advice when failing

15 files changed, 419 insertions, 294 deletions

diff --git a/builtin/am.c b/builtin/am.c
index 8aa9b5b936..739b34dcf2 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1579,47 +1579,18 @@ static int build_fake_ancestor(const struct am_state *state, const char *index_f
 }
 
 /**
- * Do the three-way merge using fake ancestor, their tree constructed
- * from the fake ancestor and the postimage of the patch, and our
- * state.
- */
-static int run_fallback_merge_recursive(const struct am_state *state,
-					unsigned char *orig_tree,
-					unsigned char *our_tree,
-					unsigned char *their_tree)
-{
-	struct child_process cp = CHILD_PROCESS_INIT;
-	int status;
-
-	cp.git_cmd = 1;
-
-	argv_array_pushf(&cp.env_array, "GITHEAD_%s=%.*s",
-			 sha1_to_hex(their_tree), linelen(state->msg), state->msg);
-	if (state->quiet)
-		argv_array_push(&cp.env_array, "GIT_MERGE_VERBOSITY=0");
-
-	argv_array_push(&cp.args, "merge-recursive");
-	argv_array_push(&cp.args, sha1_to_hex(orig_tree));
-	argv_array_push(&cp.args, "--");
-	argv_array_push(&cp.args, sha1_to_hex(our_tree));
-	argv_array_push(&cp.args, sha1_to_hex(their_tree));
-
-	status = run_command(&cp) ? (-1) : 0;
-	discard_cache();
-	read_cache();
-	return status;
-}
-
-/**
  * Attempt a threeway merge, using index_path as the temporary index.
  */
 static int fall_back_threeway(const struct am_state *state, const char *index_path)
 {
-	unsigned char orig_tree[GIT_SHA1_RAWSZ], their_tree[GIT_SHA1_RAWSZ],
-		      our_tree[GIT_SHA1_RAWSZ];
+	struct object_id orig_tree, their_tree, our_tree;
+	const struct object_id *bases[1] = { &orig_tree };
+	struct merge_options o;
+	struct commit *result;
+	char *their_tree_name;
 
-	if (get_sha1("HEAD", our_tree) < 0)
-		hashcpy(our_tree, EMPTY_TREE_SHA1_BIN);
+	if (get_oid("HEAD", &our_tree) < 0)
+		hashcpy(our_tree.hash, EMPTY_TREE_SHA1_BIN);
 
 	if (build_fake_ancestor(state, index_path))
 		return error("could not build fake ancestor");
@@ -1627,7 +1598,7 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 	discard_cache();
 	read_cache_from(index_path);
 
-	if (write_index_as_tree(orig_tree, &the_index, index_path, 0, NULL))
+	if (write_index_as_tree(orig_tree.hash, &the_index, index_path, 0, NULL))
 		return error(_("Repository lacks necessary blobs to fall back on 3-way merge."));
 
 	say(state, stdout, _("Using index info to reconstruct a base tree..."));
@@ -1643,7 +1614,7 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 		init_revisions(&rev_info, NULL);
 		rev_info.diffopt.output_format = DIFF_FORMAT_NAME_STATUS;
 		diff_opt_parse(&rev_info.diffopt, &diff_filter_str, 1, rev_info.prefix);
-		add_pending_sha1(&rev_info, "HEAD", our_tree, 0);
+		add_pending_sha1(&rev_info, "HEAD", our_tree.hash, 0);
 		diff_setup_done(&rev_info.diffopt);
 		run_diff_index(&rev_info, 1);
 	}
@@ -1652,7 +1623,7 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 		return error(_("Did you hand edit your patch?\n"
 				"It does not apply to blobs recorded in its index."));
 
-	if (write_index_as_tree(their_tree, &the_index, index_path, 0, NULL))
+	if (write_index_as_tree(their_tree.hash, &the_index, index_path, 0, NULL))
 		return error("could not write tree");
 
 	say(state, stdout, _("Falling back to patching base and 3-way merge..."));
@@ -1668,11 +1639,22 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 	 * changes.
 	 */
 
-	if (run_fallback_merge_recursive(state, orig_tree, our_tree, their_tree)) {
+	init_merge_options(&o);
+
+	o.branch1 = "HEAD";
+	their_tree_name = xstrfmt("%.*s", linelen(state->msg), state->msg);
+	o.branch2 = their_tree_name;
+
+	if (state->quiet)
+		o.verbosity = 0;
+
+	if (merge_recursive_generic(&o, &our_tree, &their_tree, 1, bases, &result)) {
 		rerere(state->allow_rerere_autoupdate);
+		free(their_tree_name);
 		return error(_("Failed to merge in the changes."));
 	}
 
+	free(their_tree_name);
 	return 0;
 }
 
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 27c1a05246..8d852d4585 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -567,10 +567,13 @@ static int merge_working_tree(const struct checkout_opts *opts,
 			o.ancestor = old->name;
 			o.branch1 = new->name;
 			o.branch2 = "local";
-			merge_trees(&o, new->commit->tree, work,
+			ret = merge_trees(&o, new->commit->tree, work,
 				old->commit->tree, &result);
+			if (ret < 0)
+				exit(128);
 			ret = reset_tree(new->commit->tree, opts, 0,
 					 writeout_error);
+			strbuf_release(&o.obuf);
 			if (ret)
 				return ret;
 		}
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index f02e3d23bb..00ea91aae6 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -118,7 +118,8 @@ static void show_killed_files(struct dir_struct *dir)
 				 */
 				pos = cache_name_pos(ent->name, ent->len);
 				if (0 <= pos)
-					die("bug in show-killed-files");
+					die("BUG: killed-file %.*s not found",
+						ent->len, ent->name);
 				pos = -pos - 1;
 				while (pos < active_nr &&
 				       ce_stage(active_cache[pos]))
diff --git a/builtin/merge.c b/builtin/merge.c
index 19b3bc2f2f..148a9a51b9 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -673,6 +673,8 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 		hold_locked_index(&lock, 1);
 		clean = merge_recursive(&o, head,
 				remoteheads->item, reversed, &result);
+		if (clean < 0)
+			exit(128);
 		if (active_cache_changed &&
 		    write_locked_index(&the_index, &lock, COMMIT_LOCK))
 			die (_("unable to write %s"), get_index_file());
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 6cdfd5f730..ba04b197d8 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -1146,7 +1146,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 		report(_("Untracked cache enabled for '%s'"), get_git_work_tree());
 		break;
 	default:
-		die("Bug: bad untracked_cache value: %d", untracked_cache);
+		die("BUG: bad untracked_cache value: %d", untracked_cache);
 	}
 
 	if (active_cache_changed) {
diff --git a/grep.c b/grep.c
index 58d599e647..d7d00b87cb 100644
--- a/grep.c
+++ b/grep.c
@@ -693,10 +693,10 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 
 	for (p = opt->header_list; p; p = p->next) {
 		if (p->token != GREP_PATTERN_HEAD)
-			die("bug: a non-header pattern in grep header list.");
+			die("BUG: a non-header pattern in grep header list.");
 		if (p->field < GREP_HEADER_FIELD_MIN ||
 		    GREP_HEADER_FIELD_MAX <= p->field)
-			die("bug: unknown header field %d", p->field);
+			die("BUG: unknown header field %d", p->field);
 		compile_regexp(p, opt);
 	}
 
@@ -709,7 +709,7 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 
 		h = compile_pattern_atom(&pp);
 		if (!h || pp != p->next)
-			die("bug: malformed header expr");
+			die("BUG: malformed header expr");
 		if (!header_group[p->field]) {
 			header_group[p->field] = h;
 			continue;
@@ -1514,7 +1514,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 		case GREP_BINARY_TEXT:
 			break;
 		default:
-			die("bug: unknown binary handling mode");
+			die("BUG: unknown binary handling mode");
 		}
 	}
 
diff --git a/imap-send.c b/imap-send.c
index db0fafee99..0f5f4760e9 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -511,7 +511,7 @@ static int nfsnprintf(char *buf, int blen, const char *fmt, ...)
 
 	va_start(va, fmt);
 	if (blen <= 0 || (unsigned)(ret = vsnprintf(buf, blen, fmt, va)) >= (unsigned)blen)
-		die("Fatal: buffer too small. Please report a bug.");
+		die("BUG: buffer too small. Please report a bug.");
 	va_end(va);
 	return ret;
 }
diff --git a/merge-recursive.c b/merge-recursive.c
index a4a1195f61..c9e4dbc349 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -23,6 +23,37 @@
 #include "dir.h"
 #include "submodule.h"
 
+static void flush_output(struct merge_options *o)
+{
+	if (o->buffer_output < 2 && o->obuf.len) {
+		fputs(o->obuf.buf, stdout);
+		strbuf_reset(&o->obuf);
+	}
+}
+
+static int err(struct merge_options *o, const char *err, ...)
+{
+	va_list params;
+
+	if (o->buffer_output < 2)
+		flush_output(o);
+	else {
+		strbuf_complete(&o->obuf, '\n');
+		strbuf_addstr(&o->obuf, "error: ");
+	}
+	va_start(params, err);
+	strbuf_vaddf(&o->obuf, err, params);
+	va_end(params);
+	if (o->buffer_output > 1)
+		strbuf_addch(&o->obuf, '\n');
+	else {
+		error("%s", o->obuf.buf);
+		strbuf_reset(&o->obuf);
+	}
+
+	return -1;
+}
+
 static struct tree *shift_tree_object(struct tree *one, struct tree *two,
 				      const char *subtree_shift)
 {
@@ -148,14 +179,6 @@ static int show(struct merge_options *o, int v)
 	return (!o->call_depth && o->verbosity >= v) || o->verbosity >= 5;
 }
 
-static void flush_output(struct merge_options *o)
-{
-	if (o->obuf.len) {
-		fputs(o->obuf.buf, stdout);
-		strbuf_reset(&o->obuf);
-	}
-}
-
 __attribute__((format (printf, 3, 4)))
 static void output(struct merge_options *o, int v, const char *fmt, ...)
 {
@@ -177,28 +200,30 @@ static void output(struct merge_options *o, int v, const char *fmt, ...)
 
 static void output_commit_title(struct merge_options *o, struct commit *commit)
 {
-	int i;
-	flush_output(o);
-	for (i = o->call_depth; i--;)
-		fputs("  ", stdout);
+	strbuf_addchars(&o->obuf, ' ', o->call_depth * 2);
 	if (commit->util)
-		printf("virtual %s\n", merge_remote_util(commit)->name);
+		strbuf_addf(&o->obuf, "virtual %s\n",
+			merge_remote_util(commit)->name);
 	else {
-		printf("%s ", find_unique_abbrev(commit->object.oid.hash, DEFAULT_ABBREV));
+		strbuf_addf(&o->obuf, "%s ",
+			find_unique_abbrev(commit->object.oid.hash,
+				DEFAULT_ABBREV));
 		if (parse_commit(commit) != 0)
-			printf(_("(bad commit)\n"));
+			strbuf_addf(&o->obuf, _("(bad commit)\n"));
 		else {
 			const char *title;
 			const char *msg = get_commit_buffer(commit, NULL);
 			int len = find_commit_subject(msg, &title);
 			if (len)
-				printf("%.*s\n", len, title);
+				strbuf_addf(&o->obuf, "%.*s\n", len, title);
 			unuse_commit_buffer(commit, msg);
 		}
 	}
+	flush_output(o);
 }
 
-static int add_cacheinfo(unsigned int mode, const struct object_id *oid,
+static int add_cacheinfo(struct merge_options *o,
+		unsigned int mode, const struct object_id *oid,
 		const char *path, int stage, int refresh, int options)
 {
 	struct cache_entry *ce;
@@ -206,7 +231,7 @@ static int add_cacheinfo(unsigned int mode, const struct object_id *oid,
 
 	ce = make_cache_entry(mode, oid ? oid->hash : null_sha1, path, stage, 0);
 	if (!ce)
-		return error(_("addinfo_cache failed for path '%s'"), path);
+		return err(o, _("addinfo_cache failed for path '%s'"), path);
 
 	ret = add_cache_entry(ce, options);
 	if (refresh) {
@@ -268,15 +293,17 @@ struct tree *write_tree_from_memory(struct merge_options *o)
 				fprintf(stderr, "BUG: %d %.*s\n", ce_stage(ce),
 					(int)ce_namelen(ce), ce->name);
 		}
-		die("Bug in merge-recursive.c");
+		die("BUG: unmerged index entries in merge-recursive.c");
 	}
 
 	if (!active_cache_tree)
 		active_cache_tree = cache_tree();
 
 	if (!cache_tree_fully_valid(active_cache_tree) &&
-	    cache_tree_update(&the_index, 0) < 0)
-		die(_("error building trees"));
+	    cache_tree_update(&the_index, 0) < 0) {
+		err(o, _("error building trees"));
+		return NULL;
+	}
 
 	result = lookup_tree(active_cache_tree->sha1);
 
@@ -542,7 +569,8 @@ static struct string_list *get_renames(struct merge_options *o,
 	return renames;
 }
 
-static int update_stages(const char *path, const struct diff_filespec *o,
+static int update_stages(struct merge_options *opt, const char *path,
+			 const struct diff_filespec *o,
 			 const struct diff_filespec *a,
 			 const struct diff_filespec *b)
 {
@@ -561,13 +589,13 @@ static int update_stages(const char *path, const struct diff_filespec *o,
 		if (remove_file_from_cache(path))
 			return -1;
 	if (o)
-		if (add_cacheinfo(o->mode, &o->oid, path, 1, 0, options))
+		if (add_cacheinfo(opt, o->mode, &o->oid, path, 1, 0, options))
 			return -1;
 	if (a)
-		if (add_cacheinfo(a->mode, &a->oid, path, 2, 0, options))
+		if (add_cacheinfo(opt, a->mode, &a->oid, path, 2, 0, options))
 			return -1;
 	if (b)
-		if (add_cacheinfo(b->mode, &b->oid, path, 3, 0, options))
+		if (add_cacheinfo(opt, b->mode, &b->oid, path, 3, 0, options))
 			return -1;
 	return 0;
 }
@@ -667,23 +695,21 @@ static int was_tracked(const char *path)
 {
 	int pos = cache_name_pos(path, strlen(path));
 
-	if (pos < 0)
-		pos = -1 - pos;
-	while (pos < active_nr &&
-	       !strcmp(path, active_cache[pos]->name)) {
-		/*
-		 * If stage #0, it is definitely tracked.
-		 * If it has stage #2 then it was tracked
-		 * before this merge started.  All other
-		 * cases the path was not tracked.
-		 */
-		switch (ce_stage(active_cache[pos])) {
-		case 0:
-		case 2:
+	if (0 <= pos)
+		/* we have been tracking this path */
+		return 1;
+
+	/*
+	 * Look for an unmerged entry for the path,
+	 * specifically stage #2, which would indicate
+	 * that "our" side before the merge started
+	 * had the path tracked (and resulted in a conflict).
+	 */
+	for (pos = -1 - pos;
+	     pos < active_nr && !strcmp(path, active_cache[pos]->name);
+	     pos++)
+		if (ce_stage(active_cache[pos]) == 2)
 			return 1;
-		}
-		pos++;
-	}
 	return 0;
 }
 
@@ -718,12 +744,10 @@ static int make_room_for_path(struct merge_options *o, const char *path)
 	/* Make sure leading directories are created */
 	status = safe_create_leading_directories_const(path);
 	if (status) {
-		if (status == SCLD_EXISTS) {
+		if (status == SCLD_EXISTS)
 			/* something else exists */
-			error(msg, path, _(": perhaps a D/F conflict?"));
-			return -1;
-		}
-		die(msg, path, "");
+			return err(o, msg, path, _(": perhaps a D/F conflict?"));
+		return err(o, msg, path, "");
 	}
 
 	/*
@@ -731,7 +755,7 @@ static int make_room_for_path(struct merge_options *o, const char *path)
 	 * tracking it.
 	 */
 	if (would_lose_untracked(path))
-		return error(_("refusing to lose untracked file at '%s'"),
+		return err(o, _("refusing to lose untracked file at '%s'"),
 			     path);
 
 	/* Successful unlink is good.. */
@@ -741,16 +765,18 @@ static int make_room_for_path(struct merge_options *o, const char *path)
 	if (errno == ENOENT)
 		return 0;
 	/* .. but not some other error (who really cares what?) */
-	return error(msg, path, _(": perhaps a D/F conflict?"));
+	return err(o, msg, path, _(": perhaps a D/F conflict?"));
 }
 
-static void update_file_flags(struct merge_options *o,
-			      const struct object_id *oid,
-			      unsigned mode,
-			      const char *path,
-			      int update_cache,
-			      int update_wd)
+static int update_file_flags(struct merge_options *o,
+			     const struct object_id *oid,
+			     unsigned mode,
+			     const char *path,
+			     int update_cache,
+			     int update_wd)
 {
+	int ret = 0;
+
 	if (o->call_depth)
 		update_wd = 0;
 
@@ -771,9 +797,11 @@ static void update_file_flags(struct merge_options *o,
 
 		buf = read_sha1_file(oid->hash, &type, &size);
 		if (!buf)
-			die(_("cannot read object %s '%s'"), oid_to_hex(oid), path);
-		if (type != OBJ_BLOB)
-			die(_("blob expected for %s '%s'"), oid_to_hex(oid), path);
+			return err(o, _("cannot read object %s '%s'"), oid_to_hex(oid), path);
+		if (type != OBJ_BLOB) {
+			ret = err(o, _("blob expected for %s '%s'"), oid_to_hex(oid), path);
+			goto free_buf;
+		}
 		if (S_ISREG(mode)) {
 			struct strbuf strbuf = STRBUF_INIT;
 			if (convert_to_working_tree(path, buf, size, &strbuf)) {
@@ -785,8 +813,7 @@ static void update_file_flags(struct merge_options *o,
 
 		if (make_room_for_path(o, path) < 0) {
 			update_wd = 0;
-			free(buf);
-			goto update_index;
+			goto free_buf;
 		}
 		if (S_ISREG(mode) || (!has_symlinks && S_ISLNK(mode))) {
 			int fd;
@@ -795,8 +822,11 @@ static void update_file_flags(struct merge_options *o,
 			else
 				mode = 0666;
 			fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
-			if (fd < 0)
-				die_errno(_("failed to open '%s'"), path);
+			if (fd < 0) {
+				ret = err(o, _("failed to open '%s': %s"),
+					  path, strerror(errno));
+				goto free_buf;
+			}
 			write_in_full(fd, buf, size);
 			close(fd);
 		} else if (S_ISLNK(mode)) {
@@ -804,25 +834,29 @@ static void update_file_flags(struct merge_options *o,
 			safe_create_leading_directories_const(path);
 			unlink(path);
 			if (symlink(lnk, path))
-				die_errno(_("failed to symlink '%s'"), path);
+				ret = err(o, _("failed to symlink '%s': %s"),
+					path, strerror(errno));
 			free(lnk);
 		} else
-			die(_("do not know what to do with %06o %s '%s'"),
-			    mode, oid_to_hex(oid), path);
+			ret = err(o,
+				  _("do not know what to do with %06o %s '%s'"),
+				  mode, oid_to_hex(oid), path);
+ free_buf:
 		free(buf);
 	}
  update_index:
-	if (update_cache)
-		add_cacheinfo(mode, oid, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
+	if (!ret && update_cache)
+		add_cacheinfo(o, mode, oid, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
+	return ret;
 }
 
-static void update_file(struct merge_options *o,
-			int clean,
-			const struct object_id *oid,
-			unsigned mode,
-			const char *path)
+static int update_file(struct merge_options *o,
+		       int clean,
+		       const struct object_id *oid,
+		       unsigned mode,
+		       const char *path)
 {
-	update_file_flags(o, oid, mode, path, o->call_depth || clean, !o->call_depth);
+	return update_file_flags(o, oid, mode, path, o->call_depth || clean, !o->call_depth);
 }
 
 /* Low level file merging, update and removal */
@@ -896,117 +930,120 @@ static int merge_3way(struct merge_options *o,
 	return merge_status;
 }
 
-static struct merge_file_info merge_file_1(struct merge_options *o,
+static int merge_file_1(struct merge_options *o,
 					   const struct diff_filespec *one,
 					   const struct diff_filespec *a,
 					   const struct diff_filespec *b,
 					   const char *branch1,
-					   const char *branch2)
+					   const char *branch2,
+					   struct merge_file_info *result)
 {
-	struct merge_file_info result;
-	result.merge = 0;
-	result.clean = 1;
+	result->merge = 0;
+	result->clean = 1;
 
 	if ((S_IFMT & a->mode) != (S_IFMT & b->mode)) {
-		result.clean = 0;
+		result->clean = 0;
 		if (S_ISREG(a->mode)) {
-			result.mode = a->mode;
-			oidcpy(&result.oid, &a->oid);
+			result->mode = a->mode;
+			oidcpy(&result->oid, &a->oid);
 		} else {
-			result.mode = b->mode;
-			oidcpy(&result.oid, &b->oid);
+			result->mode = b->mode;
+			oidcpy(&result->oid, &b->oid);
 		}
 	} else {
 		if (!oid_eq(&a->oid, &one->oid) && !oid_eq(&b->oid, &one->oid))
-			result.merge = 1;
+			result->merge = 1;
 
 		/*
 		 * Merge modes
 		 */
 		if (a->mode == b->mode || a->mode == one->mode)
-			result.mode = b->mode;
+			result->mode = b->mode;
 		else {
-			result.mode = a->mode;
+			result->mode = a->mode;
 			if (b->mode != one->mode) {
-				result.clean = 0;
-				result.merge = 1;
+				result->clean = 0;
+				result->merge = 1;
 			}
 		}
 
 		if (oid_eq(&a->oid, &b->oid) || oid_eq(&a->oid, &one->oid))
-			oidcpy(&result.oid, &b->oid);
+			oidcpy(&result->oid, &b->oid);
 		else if (oid_eq(&b->oid, &one->oid))
-			oidcpy(&result.oid, &a->oid);
+			oidcpy(&result->oid, &a->oid);
 		else if (S_ISREG(a->mode)) {
 			mmbuffer_t result_buf;
-			int merge_status;
+			int ret = 0, merge_status;
 
 			merge_status = merge_3way(o, &result_buf, one, a, b,
 						  branch1, branch2);
 
 			if ((merge_status < 0) || !result_buf.ptr)
-				die(_("Failed to execute internal merge"));
+				ret = err(o, _("Failed to execute internal merge"));
 
-			if (write_sha1_file(result_buf.ptr, result_buf.size,
-					    blob_type, result.oid.hash))
-				die(_("Unable to add %s to database"),
-				    a->path);
+			if (!ret && write_sha1_file(result_buf.ptr, result_buf.size,
+						    blob_type, result->oid.hash))
+				ret = err(o, _("Unable to add %s to database"),
+					  a->path);
 
 			free(result_buf.ptr);
-			result.clean = (merge_status == 0);
+			if (ret)
+				return ret;
+			result->clean = (merge_status == 0);
 		} else if (S_ISGITLINK(a->mode)) {
-			result.clean = merge_submodule(result.oid.hash,
+			result->clean = merge_submodule(result->oid.hash,
 						       one->path,
 						       one->oid.hash,
 						       a->oid.hash,
 						       b->oid.hash,
 						       !o->call_depth);
 		} else if (S_ISLNK(a->mode)) {
-			oidcpy(&result.oid, &a->oid);
+			oidcpy(&result->oid, &a->oid);
 
 			if (!oid_eq(&a->oid, &b->oid))
-				result.clean = 0;
-		} else {
-			die(_("unsupported object type in the tree"));
-		}
+				result->clean = 0;
+		} else
+			die("BUG: unsupported object type in the tree");
 	}
 
-	return result;
+	return 0;
 }
 
-static struct merge_file_info
-merge_file_special_markers(struct merge_options *o,
+static int merge_file_special_markers(struct merge_options *o,
 			   const struct diff_filespec *one,
 			   const struct diff_filespec *a,
 			   const struct diff_filespec *b,
 			   const char *branch1,
 			   const char *filename1,
 			   const char *branch2,
-			   const char *filename2)
+			   const char *filename2,
+			   struct merge_file_info *mfi)
 {
 	char *side1 = NULL;
 	char *side2 = NULL;
-	struct merge_file_info mfi;
+	int ret;
 
 	if (filename1)
 		side1 = xstrfmt("%s:%s", branch1, filename1);
 	if (filename2)
 		side2 = xstrfmt("%s:%s", branch2, filename2);
 
-	mfi = merge_file_1(o, one, a, b,
-			   side1 ? side1 : branch1, side2 ? side2 : branch2);
+	ret = merge_file_1(o, one, a, b,
+			   side1 ? side1 : branch1,
+			   side2 ? side2 : branch2, mfi);
 	free(side1);
 	free(side2);
-	return mfi;
+	return ret;
 }
 
-static struct merge_file_info merge_file_one(struct merge_options *o,
+static int merge_file_one(struct merge_options *o,
 					 const char *path,
 					 const struct object_id *o_oid, int o_mode,
 					 const struct object_id *a_oid, int a_mode,
 					 const struct object_id *b_oid, int b_mode,
 					 const char *branch1,
-					 const char *branch2)
+					 const char *branch2,
+					 struct merge_file_info *mfi)
 {
 	struct diff_filespec one, a, b;
 
@@ -1017,10 +1054,10 @@ static struct merge_file_info merge_file_one(struct merge_options *o,
 	a.mode = a_mode;
 	oidcpy(&b.oid, b_oid);
 	b.mode = b_mode;
-	return merge_file_1(o, &one, &a, &b, branch1, branch2);
+	return merge_file_1(o, &one, &a, &b, branch1, branch2, mfi);
 }
 
-static void handle_change_delete(struct merge_options *o,
+static int handle_change_delete(struct merge_options *o,
 				 const char *path,
 				 const struct object_id *o_oid, int o_mode,
 				 const struct object_id *a_oid, int a_mode,
@@ -1028,6 +1065,7 @@ static void handle_change_delete(struct merge_options *o,
 				 const char *change, const char *change_past)
 {
 	char *renamed = NULL;
+	int ret = 0;
 	if (dir_in_way(path, !o->call_depth)) {
 		renamed = unique_path(o, path, a_oid ? o->branch1 : o->branch2);
 	}
@@ -1038,21 +1076,23 @@ static void handle_change_delete(struct merge_options *o,
 		 * correct; since there is no true "middle point" between
 		 * them, simply reuse the base version for virtual merge base.
 		 */
-		remove_file_from_cache(path);
-		update_file(o, 0, o_oid, o_mode, renamed ? renamed : path);
+		ret = remove_file_from_cache(path);
+		if (!ret)
+			ret = update_file(o, 0, o_oid, o_mode,
+					  renamed ? renamed : path);
 	} else if (!a_oid) {
 		if (!renamed) {
 			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
 			       "and %s in %s. Version %s of %s left in tree."),
 			       change, path, o->branch1, change_past,
 			       o->branch2, o->branch2, path);
-			update_file(o, 0, b_oid, b_mode, path);
+			ret = update_file(o, 0, b_oid, b_mode, path);
 		} else {
 			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
 			       "and %s in %s. Version %s of %s left in tree at %s."),
 			       change, path, o->branch1, change_past,
 			       o->branch2, o->branch2, path, renamed);
-			update_file(o, 0, b_oid, b_mode, renamed);
+			ret = update_file(o, 0, b_oid, b_mode, renamed);
 		}
 	} else {
 		if (!renamed) {
@@ -1065,7 +1105,7 @@ static void handle_change_delete(struct merge_options *o,
 			       "and %s in %s. Version %s of %s left in tree at %s."),
 			       change, path, o->branch2, change_past,
 			       o->branch1, o->branch1, path, renamed);
-			update_file(o, 0, a_oid, a_mode, renamed);
+			ret = update_file(o, 0, a_oid, a_mode, renamed);
 		}
 		/*
 		 * No need to call update_file() on path when !renamed, since
@@ -1075,9 +1115,11 @@ static void handle_change_delete(struct merge_options *o,
 		 */
 	}
 	free(renamed);
+
+	return ret;
 }
 
-static void conflict_rename_delete(struct merge_options *o,
+static int conflict_rename_delete(struct merge_options *o,
 				   struct diff_filepair *pair,
 				   const char *rename_branch,
 				   const char *other_branch)
@@ -1097,21 +1139,20 @@ static void conflict_rename_delete(struct merge_options *o,
 		b_mode = dest->mode;
 	}
 
-	handle_change_delete(o,
-			     o->call_depth ? orig->path : dest->path,
-			     &orig->oid, orig->mode,
-			     a_oid, a_mode,
-			     b_oid, b_mode,
-			     _("rename"), _("renamed"));
-
-	if (o->call_depth) {
-		remove_file_from_cache(dest->path);
-	} else {
-		update_stages(dest->path, NULL,
-			      rename_branch == o->branch1 ? dest : NULL,
-			      rename_branch == o->branch1 ? NULL : dest);
-	}
+	if (handle_change_delete(o,
+				 o->call_depth ? orig->path : dest->path,
+				 &orig->oid, orig->mode,
+				 a_oid, a_mode,
+				 b_oid, b_mode,
+				 _("rename"), _("renamed")))
+		return -1;
 
+	if (o->call_depth)
+		return remove_file_from_cache(dest->path);
+	else
+		return update_stages(o, dest->path, NULL,
+				     rename_branch == o->branch1 ? dest : NULL,
+				     rename_branch == o->branch1 ? NULL : dest);
 }
 
 static struct diff_filespec *filespec_from_entry(struct diff_filespec *target,
@@ -1127,7 +1168,7 @@ static struct diff_filespec *filespec_from_entry(struct diff_filespec *target,
 	return target;
 }
 
-static void handle_file(struct merge_options *o,
+static int handle_file(struct merge_options *o,
 			struct diff_filespec *rename,
 			int stage,
 			struct rename_conflict_info *ci)
@@ -1137,6 +1178,7 @@ static void handle_file(struct merge_options *o,
 	const char *cur_branch, *other_branch;
 	struct diff_filespec other;
 	struct diff_filespec *add;
+	int ret;
 
 	if (stage == 2) {
 		dst_entry = ci->dst_entry1;
@@ -1151,7 +1193,8 @@ static void handle_file(struct merge_options *o,
 	add = filespec_from_entry(&other, dst_entry, stage ^ 1);
 	if (add) {
 		char *add_name = unique_path(o, rename->path, other_branch);
-		update_file(o, 0, &add->oid, add->mode, add_name);
+		if (update_file(o, 0, &add->oid, add->mode, add_name))
+			return -1;
 
 		remove_file(o, 0, rename->path, 0);
 		dst_name = unique_path(o, rename->path, cur_branch);
@@ -1162,17 +1205,20 @@ static void handle_file(struct merge_options *o,
 			       rename->path, other_branch, dst_name);
 		}
 	}
-	update_file(o, 0, &rename->oid, rename->mode, dst_name);
-	if (stage == 2)
-		update_stages(rename->path, NULL, rename, add);
+	if ((ret = update_file(o, 0, &rename->oid, rename->mode, dst_name)))
+		; /* fall through, do allow dst_name to be released */
+	else if (stage == 2)
+		ret = update_stages(o, rename->path, NULL, rename, add);
 	else
-		update_stages(rename->path, NULL, add, rename);
+		ret = update_stages(o, rename->path, NULL, add, rename);
 
 	if (dst_name != rename->path)
 		free(dst_name);
+
+	return ret;
 }
 
-static void conflict_rename_rename_1to2(struct merge_options *o,
+static int conflict_rename_rename_1to2(struct merge_options *o,
 					struct rename_conflict_info *ci)
 {
 	/* One file was renamed in both branches, but to different names. */
@@ -1190,18 +1236,21 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		struct merge_file_info mfi;
 		struct diff_filespec other;
 		struct diff_filespec *add;
-		mfi = merge_file_one(o, one->path,
+		if (merge_file_one(o, one->path,
 				 &one->oid, one->mode,
 				 &a->oid, a->mode,
 				 &b->oid, b->mode,
-				 ci->branch1, ci->branch2);
+				 ci->branch1, ci->branch2, &mfi))
+			return -1;
+
 		/*
 		 * FIXME: For rename/add-source conflicts (if we could detect
 		 * such), this is wrong.  We should instead find a unique
 		 * pathname and then either rename the add-source file to that
 		 * unique path, or use that unique path instead of src here.
 		 */
-		update_file(o, 0, &mfi.oid, mfi.mode, one->path);
+		if (update_file(o, 0, &mfi.oid, mfi.mode, one->path))
+			return -1;
 
 		/*
 		 * Above, we put the merged content at the merge-base's
@@ -1212,22 +1261,26 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		 * resolving the conflict at that path in its favor.
 		 */
 		add = filespec_from_entry(&other, ci->dst_entry1, 2 ^ 1);
-		if (add)
-			update_file(o, 0, &add->oid, add->mode, a->path);
+		if (add) {
+			if (update_file(o, 0, &add->oid, add->mode, a->path))
+				return -1;
+		}
 		else
 			remove_file_from_cache(a->path);
 		add = filespec_from_entry(&other, ci->dst_entry2, 3 ^ 1);
-		if (add)
-			update_file(o, 0, &add->oid, add->mode, b->path);
+		if (add) {
+			if (update_file(o, 0, &add->oid, add->mode, b->path))
+				return -1;
+		}
 		else
 			remove_file_from_cache(b->path);
-	} else {
-		handle_file(o, a, 2, ci);
-		handle_file(o, b, 3, ci);
-	}
+	} else if (handle_file(o, a, 2, ci) || handle_file(o, b, 3, ci))
+		return -1;
+
+	return 0;
 }
 
-static void conflict_rename_rename_2to1(struct merge_options *o,
+static int conflict_rename_rename_2to1(struct merge_options *o,
 					struct rename_conflict_info *ci)
 {
 	/* Two files, a & b, were renamed to the same thing, c. */
@@ -1238,6 +1291,7 @@ static void conflict_rename_rename_2to1(struct merge_options *o,
 	char *path = c1->path; /* == c2->path */
 	struct merge_file_info mfi_c1;
 	struct merge_file_info mfi_c2;
+	int ret;
 
 	output(o, 1, _("CONFLICT (rename/rename): "
 	       "Rename %s->%s in %s. "
@@ -1248,12 +1302,13 @@ static void conflict_rename_rename_2to1(struct merge_options *o,
 	remove_file(o, 1, a->path, o->call_depth || would_lose_untracked(a->path));
 	remove_file(o, 1, b->path, o->call_depth || would_lose_untracked(b->path));
 
-	mfi_c1 = merge_file_special_markers(o, a, c1, &ci->ren1_other,
-					    o->branch1, c1->path,
-					    o->branch2, ci->ren1_other.path);
-	mfi_c2 = merge_file_special_markers(o, b, &ci->ren2_other, c2,
-					    o->branch1, ci->ren2_other.path,
-					    o->branch2, c2->path);
+	if (merge_file_special_markers(o, a, c1, &ci->ren1_other,
+				       o->branch1, c1->path,
+				       o->branch2, ci->ren1_other.path, &mfi_c1) ||
+	    merge_file_special_markers(o, b, &ci->ren2_other, c2,
+				       o->branch1, ci->ren2_other.path,
+				       o->branch2, c2->path, &mfi_c2))
+		return -1;
 
 	if (o->call_depth) {
 		/*
@@ -1264,19 +1319,25 @@ static void conflict_rename_rename_2to1(struct merge_options *o,
 		 * again later for the non-recursive merge.
 		 */
 		remove_file(o, 0, path, 0);
-		update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, a->path);
-		update_file(o, 0, &mfi_c2.oid, mfi_c2.mode, b->path);
+		ret = update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, a->path);
+		if (!ret)
+			ret = update_file(o, 0, &mfi_c2.oid, mfi_c2.mode,
+					  b->path);
 	} else {
 		char *new_path1 = unique_path(o, path, ci->branch1);
 		char *new_path2 = unique_path(o, path, ci->branch2);
 		output(o, 1, _("Renaming %s to %s and %s to %s instead"),
 		       a->path, new_path1, b->path, new_path2);
 		remove_file(o, 0, path, 0);
-		update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, new_path1);
-		update_file(o, 0, &mfi_c2.oid, mfi_c2.mode, new_path2);
+		ret = update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, new_path1);
+		if (!ret)
+			ret = update_file(o, 0, &mfi_c2.oid, mfi_c2.mode,
+					  new_path2);
 		free(new_path2);
 		free(new_path1);
 	}
+
+	return ret;
 }
 
 static int process_renames(struct merge_options *o,
@@ -1354,7 +1415,7 @@ static int process_renames(struct merge_options *o,
 			const char *ren2_dst = ren2->pair->two->path;
 			enum rename_type rename_type;
 			if (strcmp(ren1_src, ren2_src) != 0)
-				die("ren1_src != ren2_src");
+				die("BUG: ren1_src != ren2_src");
 			ren2->dst_entry->processed = 1;
 			ren2->processed = 1;
 			if (strcmp(ren1_dst, ren2_dst) != 0) {
@@ -1388,7 +1449,7 @@ static int process_renames(struct merge_options *o,
 			ren2 = lookup->util;
 			ren2_dst = ren2->pair->two->path;
 			if (strcmp(ren1_dst, ren2_dst) != 0)
-				die("ren1_dst != ren2_dst");
+				die("BUG: ren1_dst != ren2_dst");
 
 			clean_merge = 0;
 			ren2->processed = 1;
@@ -1461,12 +1522,13 @@ static int process_renames(struct merge_options *o,
 				 * update_file_flags() instead of
 				 * update_file().
 				 */
-				update_file_flags(o,
-						  &ren1->pair->two->oid,
-						  ren1->pair->two->mode,
-						  ren1_dst,
-						  1, /* update_cache */
-						  0  /* update_wd    */);
+				if (update_file_flags(o,
+						      &ren1->pair->two->oid,
+						      ren1->pair->two->mode,
+						      ren1_dst,
+						      1, /* update_cache */
+						      0  /* update_wd    */))
+					clean_merge = -1;
 			} else if (!oid_eq(&dst_other.oid, &null_oid)) {
 				clean_merge = 0;
 				try_merge = 1;
@@ -1476,26 +1538,33 @@ static int process_renames(struct merge_options *o,
 				       ren1_dst, branch2);
 				if (o->call_depth) {
 					struct merge_file_info mfi;
-					mfi = merge_file_one(o, ren1_dst, &null_oid, 0,
-							 &ren1->pair->two->oid,
-							 ren1->pair->two->mode,
-							 &dst_other.oid,
-							 dst_other.mode,
-							 branch1, branch2);
+					if (merge_file_one(o, ren1_dst, &null_oid, 0,
+							   &ren1->pair->two->oid,
+							   ren1->pair->two->mode,
+							   &dst_other.oid,
+							   dst_other.mode,
+							   branch1, branch2, &mfi)) {
+						clean_merge = -1;
+						goto cleanup_and_return;
+					}
 					output(o, 1, _("Adding merged %s"), ren1_dst);
-					update_file(o, 0, &mfi.oid,
-						    mfi.mode, ren1_dst);
+					if (update_file(o, 0, &mfi.oid,
+							mfi.mode, ren1_dst))
+						clean_merge = -1;
 					try_merge = 0;
 				} else {
 					char *new_path = unique_path(o, ren1_dst, branch2);
 					output(o, 1, _("Adding as %s instead"), new_path);
-					update_file(o, 0, &dst_other.oid,
-						    dst_other.mode, new_path);
+					if (update_file(o, 0, &dst_other.oid,
+							dst_other.mode, new_path))
+						clean_merge = -1;
 					free(new_path);
 				}
 			} else
 				try_merge = 1;
 
+			if (clean_merge < 0)
+				goto cleanup_and_return;
 			if (try_merge) {
 				struct diff_filespec *one, *a, *b;
 				src_other.path = (char *)ren1_src;
@@ -1522,6 +1591,7 @@ static int process_renames(struct merge_options *o,
 			}
 		}
 	}
+cleanup_and_return:
 	string_list_clear(&a_by_dst, 0);
 	string_list_clear(&b_by_dst, 0);
 
@@ -1533,23 +1603,25 @@ static struct object_id *stage_oid(const struct object_id *oid, unsigned mode)
 	return (is_null_oid(oid) || mode == 0) ? NULL: (struct object_id *)oid;
 }
 
-static int read_oid_strbuf(const struct object_id *oid, struct strbuf *dst)
+static int read_oid_strbuf(struct merge_options *o,
+	const struct object_id *oid, struct strbuf *dst)
 {
 	void *buf;
 	enum object_type type;
 	unsigned long size;
 	buf = read_sha1_file(oid->hash, &type, &size);
 	if (!buf)
-		return error(_("cannot read object %s"), oid_to_hex(oid));
+		return err(o, _("cannot read object %s"), oid_to_hex(oid));
 	if (type != OBJ_BLOB) {
 		free(buf);
-		return error(_("object %s is not a blob"), oid_to_hex(oid));
+		return err(o, _("object %s is not a blob"), oid_to_hex(oid));
 	}
 	strbuf_attach(dst, buf, size, size + 1);
 	return 0;
 }
 
-static int blob_unchanged(const struct object_id *o_oid,
+static int blob_unchanged(struct merge_options *opt,
+			  const struct object_id *o_oid,
 			  unsigned o_mode,
 			  const struct object_id *a_oid,
 			  unsigned a_mode,
@@ -1567,7 +1639,7 @@ static int blob_unchanged(const struct object_id *o_oid,
 		return 0;
 
 	assert(o_oid && a_oid);
-	if (read_oid_strbuf(o_oid, &o) || read_oid_strbuf(a_oid, &a))
+	if (read_oid_strbuf(opt, o_oid, &o) || read_oid_strbuf(opt, a_oid, &a))
 		goto error_return;
 	/*
 	 * Note: binary | is used so that both renormalizations are
@@ -1584,18 +1656,18 @@ error_return:
 	return ret;
 }
 
-static void handle_modify_delete(struct merge_options *o,
+static int handle_modify_delete(struct merge_options *o,
 				 const char *path,
 				 struct object_id *o_oid, int o_mode,
 				 struct object_id *a_oid, int a_mode,
 				 struct object_id *b_oid, int b_mode)
 {
-	handle_change_delete(o,
-			     path,
-			     o_oid, o_mode,
-			     a_oid, a_mode,
-			     b_oid, b_mode,
-			     _("modify"), _("modified"));
+	return handle_change_delete(o,
+				    path,
+				    o_oid, o_mode,
+				    a_oid, a_mode,
+				    b_oid, b_mode,
+				    _("modify"), _("modified"));
 }
 
 static int merge_content(struct merge_options *o,
@@ -1639,9 +1711,10 @@ static int merge_content(struct merge_options *o,
 		if (dir_in_way(path, !o->call_depth))
 			df_conflict_remains = 1;
 	}
-	mfi = merge_file_special_markers(o, &one, &a, &b,
-					 o->branch1, path1,
-					 o->branch2, path2);
+	if (merge_file_special_markers(o, &one, &a, &b,
+				       o->branch1, path1,
+				       o->branch2, path2, &mfi))
+		return -1;
 
 	if (mfi.clean && !df_conflict_remains &&
 	    oid_eq(&mfi.oid, a_oid) && mfi.mode == a_mode) {
@@ -1655,7 +1728,7 @@ static int merge_content(struct merge_options *o,
 		 */
 		path_renamed_outside_HEAD = !path2 || !strcmp(path, path2);
 		if (!path_renamed_outside_HEAD) {
-			add_cacheinfo(mfi.mode, &mfi.oid, path,
+			add_cacheinfo(o, mfi.mode, &mfi.oid, path,
 				      0, (!o->call_depth), 0);
 			return mfi.clean;
 		}
@@ -1668,7 +1741,8 @@ static int merge_content(struct merge_options *o,
 		output(o, 1, _("CONFLICT (%s): Merge conflict in %s"),
 				reason, path);
 		if (rename_conflict_info && !df_conflict_remains)
-			update_stages(path, &one, &a, &b);
+			if (update_stages(o, path, &one, &a, &b))
+				return -1;
 	}
 
 	if (df_conflict_remains) {
@@ -1676,30 +1750,33 @@ static int merge_content(struct merge_options *o,
 		if (o->call_depth) {
 			remove_file_from_cache(path);
 		} else {
-			if (!mfi.clean)
-				update_stages(path, &one, &a, &b);
-			else {
+			if (!mfi.clean) {
+				if (update_stages(o, path, &one, &a, &b))
+					return -1;
+			} else {
 				int file_from_stage2 = was_tracked(path);
 				struct diff_filespec merged;
 				oidcpy(&merged.oid, &mfi.oid);
 				merged.mode = mfi.mode;
 
-				update_stages(path, NULL,
-					      file_from_stage2 ? &merged : NULL,
-					      file_from_stage2 ? NULL : &merged);
+				if (update_stages(o, path, NULL,
+						  file_from_stage2 ? &merged : NULL,
+						  file_from_stage2 ? NULL : &merged))
+					return -1;
 			}
 
 		}
 		new_path = unique_path(o, path, rename_conflict_info->branch1);
 		output(o, 1, _("Adding as %s instead"), new_path);
-		update_file(o, 0, &mfi.oid, mfi.mode, new_path);
+		if (update_file(o, 0, &mfi.oid, mfi.mode, new_path)) {
+			free(new_path);
+			return -1;
+		}
 		free(new_path);
 		mfi.clean = 0;
-	} else {
-		update_file(o, mfi.clean, &mfi.oid, mfi.mode, path);
-	}
+	} else if (update_file(o, mfi.clean, &mfi.oid, mfi.mode, path))
+		return -1;
 	return mfi.clean;
-
 }
 
 /* Per entry merge function */
@@ -1727,17 +1804,21 @@ static int process_entry(struct merge_options *o,
 			break;
 		case RENAME_DELETE:
 			clean_merge = 0;
-			conflict_rename_delete(o, conflict_info->pair1,
-					       conflict_info->branch1,
-					       conflict_info->branch2);
+			if (conflict_rename_delete(o,
+						   conflict_info->pair1,
+						   conflict_info->branch1,
+						   conflict_info->branch2))
+				clean_merge = -1;
 			break;
 		case RENAME_ONE_FILE_TO_TWO:
 			clean_merge = 0;
-			conflict_rename_rename_1to2(o, conflict_info);
+			if (conflict_rename_rename_1to2(o, conflict_info))
+				clean_merge = -1;
 			break;
 		case RENAME_TWO_FILES_TO_ONE:
 			clean_merge = 0;
-			conflict_rename_rename_2to1(o, conflict_info);
+			if (conflict_rename_rename_2to1(o, conflict_info))
+				clean_merge = -1;
 			break;
 		default:
 			entry->processed = 0;
@@ -1746,8 +1827,8 @@ static int process_entry(struct merge_options *o,
 	} else if (o_oid && (!a_oid || !b_oid)) {
 		/* Case A: Deleted in one */
 		if ((!a_oid && !b_oid) ||
-		    (!b_oid && blob_unchanged(o_oid, o_mode, a_oid, a_mode, normalize, path)) ||
-		    (!a_oid && blob_unchanged(o_oid, o_mode, b_oid, b_mode, normalize, path))) {
+		    (!b_oid && blob_unchanged(o, o_oid, o_mode, a_oid, a_mode, normalize, path)) ||
+		    (!a_oid && blob_unchanged(o, o_oid, o_mode, b_oid, b_mode, normalize, path))) {
 			/* Deleted in both or deleted in one and
 			 * unchanged in the other */
 			if (a_oid)
@@ -1757,8 +1838,9 @@ static int process_entry(struct merge_options *o,
 		} else {
 			/* Modify/delete; deleted side may have put a directory in the way */
 			clean_merge = 0;
-			handle_modify_delete(o, path, o_oid, o_mode,
-					     a_oid, a_mode, b_oid, b_mode);
+			if (handle_modify_delete(o, path, o_oid, o_mode,
+						 a_oid, a_mode, b_oid, b_mode))
+				clean_merge = -1;
 		}
 	} else if ((!o_oid && a_oid && !b_oid) ||
 		   (!o_oid && !a_oid && b_oid)) {
@@ -1790,14 +1872,16 @@ static int process_entry(struct merge_options *o,
 			output(o, 1, _("CONFLICT (%s): There is a directory with name %s in %s. "
 			       "Adding %s as %s"),
 			       conf, path, other_branch, path, new_path);
-			update_file(o, 0, oid, mode, new_path);
-			if (o->call_depth)
+			if (update_file(o, 0, oid, mode, new_path))
+				clean_merge = -1;
+			else if (o->call_depth)
 				remove_file_from_cache(path);
 			free(new_path);
 		} else {
 			output(o, 2, _("Adding %s"), path);
 			/* do not overwrite file if already present */
-			update_file_flags(o, oid, mode, path, 1, !a_oid);
+			if (update_file_flags(o, oid, mode, path, 1, !a_oid))
+				clean_merge = -1;
 		}
 	} else if (a_oid && b_oid) {
 		/* Case C: Added in both (check for same permissions) and */
@@ -1812,7 +1896,7 @@ static int process_entry(struct merge_options *o,
 		 */
 		remove_file(o, 1, path, !a_mode);
 	} else
-		die(_("Fatal merge failure, shouldn't happen."));
+		die("BUG: fatal merge failure, shouldn't happen.");
 
 	return clean_merge;
 }
@@ -1840,11 +1924,10 @@ int merge_trees(struct merge_options *o,
 
 	if (code != 0) {
 		if (show(o, 4) || o->call_depth)
-			die(_("merging of trees %s and %s failed"),
+			err(o, _("merging of trees %s and %s failed"),
 			    oid_to_hex(&head->object.oid),
 			    oid_to_hex(&merge->object.oid));
-		else
-			exit(128);
+		return -1;
 	}
 
 	if (unmerged_cache()) {
@@ -1860,17 +1943,23 @@ int merge_trees(struct merge_options *o,
 		re_head  = get_renames(o, head, common, head, merge, entries);
 		re_merge = get_renames(o, merge, common, head, merge, entries);
 		clean = process_renames(o, re_head, re_merge);
+		if (clean < 0)
+			return clean;
 		for (i = entries->nr-1; 0 <= i; i--) {
 			const char *path = entries->items[i].string;
 			struct stage_data *e = entries->items[i].util;
-			if (!e->processed
-				&& !process_entry(o, path, e))
-				clean = 0;
+			if (!e->processed) {
+				int ret = process_entry(o, path, e);
+				if (!ret)
+					clean = 0;
+				else if (ret < 0)
+					return ret;
+			}
 		}
 		for (i = 0; i < entries->nr; i++) {
 			struct stage_data *e = entries->items[i].util;
 			if (!e->processed)
-				die(_("Unprocessed path??? %s"),
+				die("BUG: unprocessed path??? %s",
 				    entries->items[i].string);
 		}
 
@@ -1885,8 +1974,8 @@ int merge_trees(struct merge_options *o,
 	else
 		clean = 1;
 
-	if (o->call_depth)
-		*result = write_tree_from_memory(o);
+	if (o->call_depth && !(*result = write_tree_from_memory(o)))
+		return -1;
 
 	return clean;
 }
@@ -1952,23 +2041,25 @@ int merge_recursive(struct merge_options *o,
 		/*
 		 * When the merge fails, the result contains files
 		 * with conflict markers. The cleanness flag is
-		 * ignored, it was never actually used, as result of
-		 * merge_trees has always overwritten it: the committed
-		 * "conflicts" were already resolved.
+		 * ignored (unless indicating an error), it was never
+		 * actually used, as result of merge_trees has always
+		 * overwritten it: the committed "conflicts" were
+		 * already resolved.
 		 */
 		discard_cache();
 		saved_b1 = o->branch1;
 		saved_b2 = o->branch2;
 		o->branch1 = "Temporary merge branch 1";
 		o->branch2 = "Temporary merge branch 2";
-		merge_recursive(o, merged_common_ancestors, iter->item,
-				NULL, &merged_common_ancestors);
+		if (merge_recursive(o, merged_common_ancestors, iter->item,
+				    NULL, &merged_common_ancestors) < 0)
+			return -1;
 		o->branch1 = saved_b1;
 		o->branch2 = saved_b2;
 		o->call_depth--;
 
 		if (!merged_common_ancestors)
-			die(_("merge returned no commit"));
+			return err(o, _("merge returned no commit"));
 	}
 
 	discard_cache();
@@ -1978,6 +2069,10 @@ int merge_recursive(struct merge_options *o,
 	o->ancestor = "merged common ancestors";
 	clean = merge_trees(o, h1->tree, h2->tree, merged_common_ancestors->tree,
 			    &mrtree);
+	if (clean < 0) {
+		flush_output(o);
+		return clean;
+	}
 
 	if (o->call_depth) {
 		*result = make_virtual_commit(mrtree, "merged tree");
@@ -1985,6 +2080,8 @@ int merge_recursive(struct merge_options *o,
 		commit_list_insert(h2, &(*result)->parents->next);
 	}
 	flush_output(o);
+	if (!o->call_depth && o->buffer_output < 2)
+		strbuf_release(&o->obuf);
 	if (show(o, 2))
 		diff_warn_rename_limit("merge.renamelimit",
 				       o->needed_rename_limit, 0);
@@ -2025,7 +2122,7 @@ int merge_recursive_generic(struct merge_options *o,
 		for (i = 0; i < num_base_list; ++i) {
 			struct commit *base;
 			if (!(base = get_ref(base_list[i], oid_to_hex(base_list[i]))))
-				return error(_("Could not parse object '%s'"),
+				return err(o, _("Could not parse object '%s'"),
 					oid_to_hex(base_list[i]));
 			commit_list_insert(base, &ca);
 		}
@@ -2034,9 +2131,12 @@ int merge_recursive_generic(struct merge_options *o,
 	hold_locked_index(lock, 1);
 	clean = merge_recursive(o, head_commit, next_commit, ca,
 			result);
+	if (clean < 0)
+		return clean;
+
 	if (active_cache_changed &&
 	    write_locked_index(&the_index, lock, COMMIT_LOCK))
-		return error(_("Unable to write index."));
+		return err(o, _("Unable to write index."));
 
 	return clean ? 0 : 1;
 }
diff --git a/merge-recursive.h b/merge-recursive.h
index d415724aea..735343b413 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -13,7 +13,7 @@ struct merge_options {
 		MERGE_RECURSIVE_THEIRS
 	} recursive_variant;
 	const char *subtree_shift;
-	unsigned buffer_output : 1;
+	unsigned buffer_output; /* 1: output at end, 2: keep buffered */
 	unsigned renormalize : 1;
 	long xdl_opts;
 	int verbosity;
diff --git a/sequencer.c b/sequencer.c
index 7b1eb14645..2e9c7d0f03 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -293,6 +293,9 @@ static int do_recursive_merge(struct commit *base, struct commit *next,
 	clean = merge_trees(&o,
 			    head_tree,
 			    next_tree, base_tree, &result);
+	strbuf_release(&o.obuf);
+	if (clean < 0)
+		return clean;
 
 	if (active_cache_changed &&
 	    write_locked_index(&the_index, &index_lock, COMMIT_LOCK))
@@ -559,6 +562,8 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 	if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REPLAY_REVERT) {
 		res = do_recursive_merge(base, next, base_label, next_label,
 					 head, &msgbuf, opts);
+		if (res < 0)
+			return res;
 		write_message(&msgbuf, git_path_merge_msg());
 	} else {
 		struct commit_list *common = NULL;
diff --git a/sha1_file.c b/sha1_file.c
index 3066b5f71c..02940f1920 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -791,7 +791,7 @@ void close_all_packs(void)
 
 	for (p = packed_git; p; p = p->next)
 		if (p->do_not_close)
-			die("BUG! Want to close pack marked 'do-not-close'");
+			die("BUG: want to close pack marked 'do-not-close'");
 		else
 			close_pack(p);
 }
@@ -2306,7 +2306,7 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 	case OBJ_OFS_DELTA:
 	case OBJ_REF_DELTA:
 		if (data)
-			die("BUG in unpack_entry: left loop at a valid delta");
+			die("BUG: unpack_entry: left loop at a valid delta");
 		break;
 	case OBJ_COMMIT:
 	case OBJ_TREE:
diff --git a/t/t5520-pull.sh b/t/t5520-pull.sh
index 37ebbcfbbf..6ad37b5f66 100755
--- a/t/t5520-pull.sh
+++ b/t/t5520-pull.sh
@@ -255,6 +255,38 @@ test_expect_success '--rebase' '
 	test new = "$(git show HEAD:file2)"
 '
 
+test_expect_success '--rebase with conflicts shows advice' '
+	test_when_finished "git rebase --abort; git checkout -f to-rebase" &&
+	git checkout -b seq &&
+	test_seq 5 >seq.txt &&
+	git add seq.txt &&
+	test_tick &&
+	git commit -m "Add seq.txt" &&
+	echo 6 >>seq.txt &&
+	test_tick &&
+	git commit -m "Append to seq.txt" seq.txt &&
+	git checkout -b with-conflicts HEAD^ &&
+	echo conflicting >>seq.txt &&
+	test_tick &&
+	git commit -m "Create conflict" seq.txt &&
+	test_must_fail git pull --rebase . seq 2>err >out &&
+	grep "When you have resolved this problem" out
+'
+
+test_expect_success 'failed --rebase shows advice' '
+	test_when_finished "git rebase --abort; git checkout -f to-rebase" &&
+	git checkout -b diverging &&
+	test_commit attributes .gitattributes "* text=auto" attrs &&
+	sha1="$(printf "1\\r\\n" | git hash-object -w --stdin)" &&
+	git update-index --cacheinfo 0644 $sha1 file &&
+	git commit -m v1-with-cr &&
+	# force checkout because `git reset --hard` will not leave clean `file`
+	git checkout -f -b fails-to-rebase HEAD^ &&
+	test_commit v2-without-cr file "2" file2-lf &&
+	test_must_fail git pull --rebase . diverging 2>err >out &&
+	grep "When you have resolved this problem" out
+'
+
 test_expect_success '--rebase fails with multiple branches' '
 	git reset --hard before-rebase &&
 	test_must_fail git pull --rebase . copy master 2>err &&
diff --git a/trailer.c b/trailer.c
index 8e48a5c990..c6ea9ac64d 100644
--- a/trailer.c
+++ b/trailer.c
@@ -562,7 +562,7 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
 			warning(_("unknown value '%s' for key '%s'"), value, conf_key);
 		break;
 	default:
-		die("internal bug in trailer.c");
+		die("BUG: trailer.c: unhandled type %d", type);
 	}
 	return 0;
 }
diff --git a/transport.c b/transport.c
index 4ba48b0596..c5772a14ee 100644
--- a/transport.c
+++ b/transport.c
@@ -567,7 +567,7 @@ void transport_take_over(struct transport *transport,
 	struct git_transport_data *data;
 
 	if (!transport->smart_options)
-		die("Bug detected: Taking over transport requires non-NULL "
+		die("BUG: taking over transport requires non-NULL "
 		    "smart_options field.");
 
 	data = xcalloc(1, sizeof(*data));
diff --git a/wt-status.c b/wt-status.c
index 3175ec6ddb..6225a2d89f 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -263,7 +263,7 @@ static const char *wt_status_unmerged_status_string(int stagemask)
 	case 7:
 		return _("both modified:");
 	default:
-		die("bug: unhandled unmerged status %x", stagemask);
+		die("BUG: unhandled unmerged status %x", stagemask);
 	}
 }
 
@@ -388,7 +388,7 @@ static void wt_status_print_change_data(struct wt_status *s,
 	status_printf(s, color(WT_STATUS_HEADER, s), "\t");
 	what = wt_status_diff_status_string(status);
 	if (!what)
-		die("bug: unhandled diff status %c", status);
+		die("BUG: unhandled diff status %c", status);
 	len = label_width - utf8_strwidth(what);
 	assert(len >= 0);
 	if (status == DIFF_STATUS_COPIED || status == DIFF_STATUS_RENAMED)