fmt-merge-msg: use branch.$name.description

This teaches "merge --log" and fmt-merge-msg to use branch description
information when merging a local topic branch into the mainline. The
description goes between the branch name label and the list of commit
titles.

The refactoring to share the common configuration parsing between
merge and fmt-merge-msg needs to be made into a separate patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 78 insertions, 26 deletions

diff --git a/Makefile b/Makefile
index 8d6d4515d2..b499049ae7 100644
--- a/Makefile
+++ b/Makefile
@@ -527,6 +527,7 @@ LIB_H += diffcore.h
 LIB_H += diff.h
 LIB_H += dir.h
 LIB_H += exec_cmd.h
+LIB_H += fmt-merge-msg.h
 LIB_H += fsck.h
 LIB_H += gettext.h
 LIB_H += git-compat-util.h
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 75816329d6..1350462d43 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -5,23 +5,27 @@
 #include "revision.h"
 #include "tag.h"
 #include "string-list.h"
+#include "branch.h"
+#include "fmt-merge-msg.h"
 
 static const char * const fmt_merge_msg_usage[] = {
 	"git fmt-merge-msg [-m <message>] [--log[=<n>]|--no-log] [--file <file>]",
 	NULL
 };
 
-static int shortlog_len;
+static int use_branch_desc;
 
-static int fmt_merge_msg_config(const char *key, const char *value, void *cb)
+int fmt_merge_msg_config(const char *key, const char *value, void *cb)
 {
 	if (!strcmp(key, "merge.log") || !strcmp(key, "merge.summary")) {
 		int is_bool;
-		shortlog_len = git_config_bool_or_int(key, value, &is_bool);
-		if (!is_bool && shortlog_len < 0)
+		merge_log_config = git_config_bool_or_int(key, value, &is_bool);
+		if (!is_bool && merge_log_config < 0)
 			return error("%s: negative length %s", key, value);
-		if (is_bool && shortlog_len)
-			shortlog_len = DEFAULT_MERGE_LOG_LEN;
+		if (is_bool && merge_log_config)
+			merge_log_config = DEFAULT_MERGE_LOG_LEN;
+	} else if (!strcmp(key, "merge.branchdesc")) {
+		use_branch_desc = git_config_bool(key, value);
 	}
 	return 0;
 }
@@ -31,6 +35,11 @@ struct src_data {
 	int head_status;
 };
 
+struct origin_data {
+	unsigned char sha1[20];
+	int is_local_branch:1;
+};
+
 static void init_src_data(struct src_data *data)
 {
 	data->branch.strdup_strings = 1;
@@ -45,7 +54,7 @@ static struct string_list origins = STRING_LIST_INIT_DUP;
 static int handle_line(char *line)
 {
 	int i, len = strlen(line);
-	unsigned char *sha1;
+	struct origin_data *origin_data;
 	char *src, *origin;
 	struct src_data *src_data;
 	struct string_list_item *item;
@@ -61,11 +70,13 @@ static int handle_line(char *line)
 		return 2;
 
 	line[40] = 0;
-	sha1 = xmalloc(20);
-	i = get_sha1(line, sha1);
+	origin_data = xcalloc(1, sizeof(struct origin_data));
+	i = get_sha1(line, origin_data->sha1);
 	line[40] = '\t';
-	if (i)
+	if (i) {
+		free(origin_data);
 		return 3;
+	}
 
 	if (line[len - 1] == '\n')
 		line[len - 1] = 0;
@@ -93,6 +104,7 @@ static int handle_line(char *line)
 		origin = src;
 		src_data->head_status |= 1;
 	} else if (!prefixcmp(line, "branch ")) {
+		origin_data->is_local_branch = 1;
 		origin = line + 7;
 		string_list_append(&src_data->branch, origin);
 		src_data->head_status |= 2;
@@ -119,7 +131,9 @@ static int handle_line(char *line)
 		sprintf(new_origin, "%s of %s", origin, src);
 		origin = new_origin;
 	}
-	string_list_append(&origins, origin)->util = sha1;
+	if (strcmp(".", src))
+		origin_data->is_local_branch = 0;
+	string_list_append(&origins, origin)->util = origin_data;
 	return 0;
 }
 
@@ -140,9 +154,30 @@ static void print_joined(const char *singular, const char *plural,
 	}
 }
 
-static void shortlog(const char *name, unsigned char *sha1,
-		struct commit *head, struct rev_info *rev, int limit,
-		struct strbuf *out)
+static void add_branch_desc(struct strbuf *out, const char *name)
+{
+	struct strbuf desc = STRBUF_INIT;
+
+	if (!read_branch_desc(&desc, name)) {
+		const char *bp = desc.buf;
+		while (*bp) {
+			const char *ep = strchrnul(bp, '\n');
+			if (*ep)
+				ep++;
+			strbuf_addf(out, "  : %.*s", (int)(ep - bp), bp);
+			bp = ep;
+		}
+		if (out->buf[out->len - 1] != '\n')
+			strbuf_addch(out, '\n');
+	}
+	strbuf_release(&desc);
+}
+
+static void shortlog(const char *name,
+		     struct origin_data *origin_data,
+		     struct commit *head,
+		     struct rev_info *rev, int limit,
+		     struct strbuf *out)
 {
 	int i, count = 0;
 	struct commit *commit;
@@ -150,6 +185,7 @@ static void shortlog(const char *name, unsigned char *sha1,
 	struct string_list subjects = STRING_LIST_INIT_DUP;
 	int flags = UNINTERESTING | TREESAME | SEEN | SHOWN | ADDED;
 	struct strbuf sb = STRBUF_INIT;
+	const unsigned char *sha1 = origin_data->sha1;
 
 	branch = deref_tag(parse_object(sha1), sha1_to_hex(sha1), 40);
 	if (!branch || branch->type != OBJ_COMMIT)
@@ -188,6 +224,9 @@ static void shortlog(const char *name, unsigned char *sha1,
 	else
 		strbuf_addf(out, "\n* %s:\n", name);
 
+	if (origin_data->is_local_branch && use_branch_desc)
+		add_branch_desc(out, name);
+
 	for (i = 0; i < subjects.nr; i++)
 		if (i >= limit)
 			strbuf_addf(out, "  ...\n");
@@ -303,8 +342,9 @@ static int do_fmt_merge_msg(int merge_title, struct strbuf *in,
 			strbuf_addch(out, '\n');
 
 		for (i = 0; i < origins.nr; i++)
-			shortlog(origins.items[i].string, origins.items[i].util,
-					head, &rev, shortlog_len, out);
+			shortlog(origins.items[i].string,
+				 origins.items[i].util,
+				 head, &rev, shortlog_len, out);
 	}
 	return 0;
 }
@@ -318,6 +358,7 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 {
 	const char *inpath = NULL;
 	const char *message = NULL;
+	int shortlog_len = -1;
 	struct option options[] = {
 		{ OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 		  "populate log with at most <n> entries from shortlog",
@@ -341,6 +382,8 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 			     0);
 	if (argc > 0)
 		usage_with_options(fmt_merge_msg_usage, options);
+	if (shortlog_len < 0)
+		shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
 	if (message && !shortlog_len) {
 		char nl = '\n';
 		write_in_full(STDOUT_FILENO, message, strlen(message));
diff --git a/builtin/merge.c b/builtin/merge.c
index ab4077f272..b8f25dd44e 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -26,6 +26,7 @@
 #include "merge-recursive.h"
 #include "resolve-undo.h"
 #include "remote.h"
+#include "fmt-merge-msg.h"
 
 #define DEFAULT_TWOHEAD (1<<0)
 #define DEFAULT_OCTOPUS (1<<1)
@@ -44,7 +45,7 @@ static const char * const builtin_merge_usage[] = {
 	NULL
 };
 
-static int show_diffstat = 1, shortlog_len, squash;
+static int show_diffstat = 1, shortlog_len = -1, squash;
 static int option_commit = 1, allow_fast_forward = 1;
 static int fast_forward_only;
 static int allow_trivial = 1, have_message;
@@ -525,6 +526,8 @@ static void parse_branch_merge_options(char *bmo)
 
 static int git_merge_config(const char *k, const char *v, void *cb)
 {
+	int status;
+
 	if (branch && !prefixcmp(k, "branch.") &&
 		!prefixcmp(k + 7, branch) &&
 		!strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
@@ -541,15 +544,7 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		return git_config_string(&pull_octopus, k, v);
 	else if (!strcmp(k, "merge.renormalize"))
 		option_renormalize = git_config_bool(k, v);
-	else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
-		int is_bool;
-		shortlog_len = git_config_bool_or_int(k, v, &is_bool);
-		if (!is_bool && shortlog_len < 0)
-			return error(_("%s: negative length %s"), k, v);
-		if (is_bool && shortlog_len)
-			shortlog_len = DEFAULT_MERGE_LOG_LEN;
-		return 0;
-	} else if (!strcmp(k, "merge.ff")) {
+	else if (!strcmp(k, "merge.ff")) {
 		int boolval = git_config_maybe_bool(k, v);
 		if (0 <= boolval) {
 			allow_fast_forward = boolval;
@@ -562,6 +557,9 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		default_to_upstream = git_config_bool(k, v);
 		return 0;
 	}
+	status = fmt_merge_msg_config(k, v, cb);
+	if (status)
+		return status;
 	return git_diff_ui_config(k, v, cb);
 }
 
@@ -1035,6 +1033,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		parse_branch_merge_options(branch_mergeoptions);
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
+	if (shortlog_len < 0)
+		shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
 
 	if (verbosity < 0 && show_progress == -1)
 		show_progress = 0;
diff --git a/environment.c b/environment.c
index e96edcfebc..ba9781b713 100644
--- a/environment.c
+++ b/environment.c
@@ -58,6 +58,7 @@ enum object_creation_mode object_creation_mode = OBJECT_CREATION_MODE;
 char *notes_ref_name;
 int grafts_replace_parents = 1;
 int core_apply_sparse_checkout;
+int merge_log_config = -1;
 struct startup_info *startup_info;
 
 /* Parallel index stat data preload? */
diff --git a/fmt-merge-msg.h b/fmt-merge-msg.h
new file mode 100644
index 0000000000..b28d3a6113
--- /dev/null
+++ b/fmt-merge-msg.h
@@ -0,0 +1,7 @@
+#ifndef FMT_MERGE_MSG_H
+#define FMT_MERGE_MSG_H
+
+extern int merge_log_config;
+extern int fmt_merge_msg_config(const char *key, const char *value, void *cb);
+
+#endif /* FMT_MERGE_MSG_H */