Merge branch 'bw/grep-recurse-submodules'

"git grep" has been taught to optionally recurse into submodules.

* bw/grep-recurse-submodules:
  grep: search history of moved submodules
  grep: enable recurse-submodules to work on <tree> objects
  grep: optionally recurse into submodules
  grep: add submodules as a grep source type
  submodules: load gitmodules file from commit sha1
  submodules: add helper to determine if a submodule is initialized
  submodules: add helper to determine if a submodule is populated
  real_path: canonicalize directory separators in root parts
  real_path: have callers use real_pathdup and strbuf_realpath
  real_path: create real_pathdup
  real_path: convert real_path_internal to strbuf_realpath
  real_path: resolve symlinks by hand

20 files changed, 904 insertions, 117 deletions

diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index 0ecea6e491..71f32f3508 100644
--- a/Documentation/git-grep.txt
+++ b/Documentation/git-grep.txt
@@ -26,6 +26,7 @@ SYNOPSIS
 	   [--threads <num>]
 	   [-f <file>] [-e] <pattern>
 	   [--and|--or|--not|(|)|-e <pattern>...]
+	   [--recurse-submodules] [--parent-basename <basename>]
 	   [ [--[no-]exclude-standard] [--cached | --no-index | --untracked] | <tree>...]
 	   [--] [<pathspec>...]
 
@@ -88,6 +89,19 @@ OPTIONS
 	mechanism.  Only useful when searching files in the current directory
 	with `--no-index`.
 
+--recurse-submodules::
+	Recursively search in each submodule that has been initialized and
+	checked out in the repository.  When used in combination with the
+	<tree> option the prefix of all submodule output will be the name of
+	the parent project's <tree> object.
+
+--parent-basename <basename>::
+	For internal use only.  In order to produce uniform output with the
+	--recurse-submodules option, this option can be used to provide the
+	basename of a parent's <tree> object to a submodule so the submodule
+	can prefix its output with the parent's name rather than the SHA1 of
+	the submodule.
+
 -a::
 --text::
 	Process binary files as if they were text.
diff --git a/abspath.c b/abspath.c
index 2825de8591..1d56f5ed9f 100644
--- a/abspath.c
+++ b/abspath.c
@@ -11,46 +11,81 @@ int is_directory(const char *path)
 	return (!stat(path, &st) && S_ISDIR(st.st_mode));
 }
 
+/* removes the last path component from 'path' except if 'path' is root */
+static void strip_last_component(struct strbuf *path)
+{
+	size_t offset = offset_1st_component(path->buf);
+	size_t len = path->len;
+
+	/* Find start of the last component */
+	while (offset < len && !is_dir_sep(path->buf[len - 1]))
+		len--;
+	/* Skip sequences of multiple path-separators */
+	while (offset < len && is_dir_sep(path->buf[len - 1]))
+		len--;
+
+	strbuf_setlen(path, len);
+}
+
+/* get (and remove) the next component in 'remaining' and place it in 'next' */
+static void get_next_component(struct strbuf *next, struct strbuf *remaining)
+{
+	char *start = NULL;
+	char *end = NULL;
+
+	strbuf_reset(next);
+
+	/* look for the next component */
+	/* Skip sequences of multiple path-separators */
+	for (start = remaining->buf; is_dir_sep(*start); start++)
+		; /* nothing */
+	/* Find end of the path component */
+	for (end = start; *end && !is_dir_sep(*end); end++)
+		; /* nothing */
+
+	strbuf_add(next, start, end - start);
+	/* remove the component from 'remaining' */
+	strbuf_remove(remaining, 0, end - remaining->buf);
+}
+
+/* copies root part from remaining to resolved, canonicalizing it on the way */
+static void get_root_part(struct strbuf *resolved, struct strbuf *remaining)
+{
+	int offset = offset_1st_component(remaining->buf);
+
+	strbuf_reset(resolved);
+	strbuf_add(resolved, remaining->buf, offset);
+#ifdef GIT_WINDOWS_NATIVE
+	convert_slashes(resolved->buf);
+#endif
+	strbuf_remove(remaining, 0, offset);
+}
+
 /* We allow "recursive" symbolic links. Only within reason, though. */
-#define MAXDEPTH 5
+#define MAXSYMLINKS 5
 
 /*
  * Return the real path (i.e., absolute path, with symlinks resolved
  * and extra slashes removed) equivalent to the specified path.  (If
  * you want an absolute path but don't mind links, use
- * absolute_path().)  The return value is a pointer to a static
- * buffer.
+ * absolute_path().)  Places the resolved realpath in the provided strbuf.
  *
- * The input and all intermediate paths must be shorter than MAX_PATH.
  * The directory part of path (i.e., everything up to the last
  * dir_sep) must denote a valid, existing directory, but the last
  * component need not exist.  If die_on_error is set, then die with an
  * informative error message if there is a problem.  Otherwise, return
  * NULL on errors (without generating any output).
- *
- * If path is our buffer, then return path, as it's already what the
- * user wants.
  */
-static const char *real_path_internal(const char *path, int die_on_error)
+char *strbuf_realpath(struct strbuf *resolved, const char *path,
+		      int die_on_error)
 {
-	static struct strbuf sb = STRBUF_INIT;
+	struct strbuf remaining = STRBUF_INIT;
+	struct strbuf next = STRBUF_INIT;
+	struct strbuf symlink = STRBUF_INIT;
 	char *retval = NULL;
-
-	/*
-	 * If we have to temporarily chdir(), store the original CWD
-	 * here so that we can chdir() back to it at the end of the
-	 * function:
-	 */
-	struct strbuf cwd = STRBUF_INIT;
-
-	int depth = MAXDEPTH;
-	char *last_elem = NULL;
+	int num_symlinks = 0;
 	struct stat st;
 
-	/* We've already done it */
-	if (path == sb.buf)
-		return path;
-
 	if (!*path) {
 		if (die_on_error)
 			die("The empty string is not a valid path");
@@ -58,86 +93,134 @@ static const char *real_path_internal(const char *path, int die_on_error)
 			goto error_out;
 	}
 
-	strbuf_reset(&sb);
-	strbuf_addstr(&sb, path);
-
-	while (depth--) {
-		if (!is_directory(sb.buf)) {
-			char *last_slash = find_last_dir_sep(sb.buf);
-			if (last_slash) {
-				last_elem = xstrdup(last_slash + 1);
-				strbuf_setlen(&sb, last_slash - sb.buf + 1);
-			} else {
-				last_elem = xmemdupz(sb.buf, sb.len);
-				strbuf_reset(&sb);
-			}
+	strbuf_addstr(&remaining, path);
+	get_root_part(resolved, &remaining);
+
+	if (!resolved->len) {
+		/* relative path; can use CWD as the initial resolved path */
+		if (strbuf_getcwd(resolved)) {
+			if (die_on_error)
+				die_errno("unable to get current working directory");
+			else
+				goto error_out;
 		}
+	}
 
-		if (sb.len) {
-			if (!cwd.len && strbuf_getcwd(&cwd)) {
+	/* Iterate over the remaining path components */
+	while (remaining.len > 0) {
+		get_next_component(&next, &remaining);
+
+		if (next.len == 0) {
+			continue; /* empty component */
+		} else if (next.len == 1 && !strcmp(next.buf, ".")) {
+			continue; /* '.' component */
+		} else if (next.len == 2 && !strcmp(next.buf, "..")) {
+			/* '..' component; strip the last path component */
+			strip_last_component(resolved);
+			continue;
+		}
+
+		/* append the next component and resolve resultant path */
+		if (!is_dir_sep(resolved->buf[resolved->len - 1]))
+			strbuf_addch(resolved, '/');
+		strbuf_addbuf(resolved, &next);
+
+		if (lstat(resolved->buf, &st)) {
+			/* error out unless this was the last component */
+			if (errno != ENOENT || remaining.len) {
 				if (die_on_error)
-					die_errno("Could not get current working directory");
+					die_errno("Invalid path '%s'",
+						  resolved->buf);
 				else
 					goto error_out;
 			}
+		} else if (S_ISLNK(st.st_mode)) {
+			ssize_t len;
+			strbuf_reset(&symlink);
 
-			if (chdir(sb.buf)) {
+			if (num_symlinks++ > MAXSYMLINKS) {
 				if (die_on_error)
-					die_errno("Could not switch to '%s'",
-						  sb.buf);
+					die("More than %d nested symlinks "
+					    "on path '%s'", MAXSYMLINKS, path);
 				else
 					goto error_out;
 			}
-		}
-		if (strbuf_getcwd(&sb)) {
-			if (die_on_error)
-				die_errno("Could not get current working directory");
-			else
-				goto error_out;
-		}
-
-		if (last_elem) {
-			if (sb.len && !is_dir_sep(sb.buf[sb.len - 1]))
-				strbuf_addch(&sb, '/');
-			strbuf_addstr(&sb, last_elem);
-			free(last_elem);
-			last_elem = NULL;
-		}
 
-		if (!lstat(sb.buf, &st) && S_ISLNK(st.st_mode)) {
-			struct strbuf next_sb = STRBUF_INIT;
-			ssize_t len = strbuf_readlink(&next_sb, sb.buf, 0);
+			len = strbuf_readlink(&symlink, resolved->buf,
+					      st.st_size);
 			if (len < 0) {
 				if (die_on_error)
 					die_errno("Invalid symlink '%s'",
-						  sb.buf);
+						  resolved->buf);
 				else
 					goto error_out;
 			}
-			strbuf_swap(&sb, &next_sb);
-			strbuf_release(&next_sb);
-		} else
-			break;
+
+			if (is_absolute_path(symlink.buf)) {
+				/* absolute symlink; set resolved to root */
+				get_root_part(resolved, &symlink);
+			} else {
+				/*
+				 * relative symlink
+				 * strip off the last component since it will
+				 * be replaced with the contents of the symlink
+				 */
+				strip_last_component(resolved);
+			}
+
+			/*
+			 * if there are still remaining components to resolve
+			 * then append them to symlink
+			 */
+			if (remaining.len) {
+				strbuf_addch(&symlink, '/');
+				strbuf_addbuf(&symlink, &remaining);
+			}
+
+			/*
+			 * use the symlink as the remaining components that
+			 * need to be resloved
+			 */
+			strbuf_swap(&symlink, &remaining);
+		}
 	}
 
-	retval = sb.buf;
+	retval = resolved->buf;
+
 error_out:
-	free(last_elem);
-	if (cwd.len && chdir(cwd.buf))
-		die_errno("Could not change back to '%s'", cwd.buf);
-	strbuf_release(&cwd);
+	strbuf_release(&remaining);
+	strbuf_release(&next);
+	strbuf_release(&symlink);
+
+	if (!retval)
+		strbuf_reset(resolved);
 
 	return retval;
 }
 
 const char *real_path(const char *path)
 {
-	return real_path_internal(path, 1);
+	static struct strbuf realpath = STRBUF_INIT;
+	return strbuf_realpath(&realpath, path, 1);
 }
 
 const char *real_path_if_valid(const char *path)
 {
-	return real_path_internal(path, 0);
+	static struct strbuf realpath = STRBUF_INIT;
+	return strbuf_realpath(&realpath, path, 0);
+}
+
+char *real_pathdup(const char *path)
+{
+	struct strbuf realpath = STRBUF_INIT;
+	char *retval = NULL;
+
+	if (strbuf_realpath(&realpath, path, 0))
+		retval = strbuf_detach(&realpath, NULL);
+
+	strbuf_release(&realpath);
+
+	return retval;
 }
 
 /*
diff --git a/builtin/grep.c b/builtin/grep.c
index 8887b6addb..2c727ef499 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -18,12 +18,22 @@
 #include "quote.h"
 #include "dir.h"
 #include "pathspec.h"
+#include "submodule.h"
+#include "submodule-config.h"
 
 static char const * const grep_usage[] = {
 	N_("git grep [<options>] [-e] <pattern> [<rev>...] [[--] <path>...]"),
 	NULL
 };
 
+static const char *super_prefix;
+static int recurse_submodules;
+static struct argv_array submodule_options = ARGV_ARRAY_INIT;
+static const char *parent_basename;
+
+static int grep_submodule_launch(struct grep_opt *opt,
+				 const struct grep_source *gs);
+
 #define GREP_NUM_THREADS_DEFAULT 8
 static int num_threads;
 
@@ -174,7 +184,10 @@ static void *run(void *arg)
 			break;
 
 		opt->output_priv = w;
-		hit |= grep_source(opt, &w->source);
+		if (w->source.type == GREP_SOURCE_SUBMODULE)
+			hit |= grep_submodule_launch(opt, &w->source);
+		else
+			hit |= grep_source(opt, &w->source);
 		grep_source_clear_data(&w->source);
 		work_done(w);
 	}
@@ -300,6 +313,10 @@ static int grep_sha1(struct grep_opt *opt, const unsigned char *sha1,
 	if (opt->relative && opt->prefix_length) {
 		quote_path_relative(filename + tree_name_len, opt->prefix, &pathbuf);
 		strbuf_insert(&pathbuf, 0, filename, tree_name_len);
+	} else if (super_prefix) {
+		strbuf_add(&pathbuf, filename, tree_name_len);
+		strbuf_addstr(&pathbuf, super_prefix);
+		strbuf_addstr(&pathbuf, filename + tree_name_len);
 	} else {
 		strbuf_addstr(&pathbuf, filename);
 	}
@@ -328,10 +345,13 @@ static int grep_file(struct grep_opt *opt, const char *filename)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (opt->relative && opt->prefix_length)
+	if (opt->relative && opt->prefix_length) {
 		quote_path_relative(filename, opt->prefix, &buf);
-	else
+	} else {
+		if (super_prefix)
+			strbuf_addstr(&buf, super_prefix);
 		strbuf_addstr(&buf, filename);
+	}
 
 #ifndef NO_PTHREADS
 	if (num_threads) {
@@ -378,31 +398,310 @@ static void run_pager(struct grep_opt *opt, const char *prefix)
 		exit(status);
 }
 
-static int grep_cache(struct grep_opt *opt, const struct pathspec *pathspec, int cached)
+static void compile_submodule_options(const struct grep_opt *opt,
+				      const struct pathspec *pathspec,
+				      int cached, int untracked,
+				      int opt_exclude, int use_index,
+				      int pattern_type_arg)
+{
+	struct grep_pat *pattern;
+	int i;
+
+	if (recurse_submodules)
+		argv_array_push(&submodule_options, "--recurse-submodules");
+
+	if (cached)
+		argv_array_push(&submodule_options, "--cached");
+	if (!use_index)
+		argv_array_push(&submodule_options, "--no-index");
+	if (untracked)
+		argv_array_push(&submodule_options, "--untracked");
+	if (opt_exclude > 0)
+		argv_array_push(&submodule_options, "--exclude-standard");
+
+	if (opt->invert)
+		argv_array_push(&submodule_options, "-v");
+	if (opt->ignore_case)
+		argv_array_push(&submodule_options, "-i");
+	if (opt->word_regexp)
+		argv_array_push(&submodule_options, "-w");
+	switch (opt->binary) {
+	case GREP_BINARY_NOMATCH:
+		argv_array_push(&submodule_options, "-I");
+		break;
+	case GREP_BINARY_TEXT:
+		argv_array_push(&submodule_options, "-a");
+		break;
+	default:
+		break;
+	}
+	if (opt->allow_textconv)
+		argv_array_push(&submodule_options, "--textconv");
+	if (opt->max_depth != -1)
+		argv_array_pushf(&submodule_options, "--max-depth=%d",
+				 opt->max_depth);
+	if (opt->linenum)
+		argv_array_push(&submodule_options, "-n");
+	if (!opt->pathname)
+		argv_array_push(&submodule_options, "-h");
+	if (!opt->relative)
+		argv_array_push(&submodule_options, "--full-name");
+	if (opt->name_only)
+		argv_array_push(&submodule_options, "-l");
+	if (opt->unmatch_name_only)
+		argv_array_push(&submodule_options, "-L");
+	if (opt->null_following_name)
+		argv_array_push(&submodule_options, "-z");
+	if (opt->count)
+		argv_array_push(&submodule_options, "-c");
+	if (opt->file_break)
+		argv_array_push(&submodule_options, "--break");
+	if (opt->heading)
+		argv_array_push(&submodule_options, "--heading");
+	if (opt->pre_context)
+		argv_array_pushf(&submodule_options, "--before-context=%d",
+				 opt->pre_context);
+	if (opt->post_context)
+		argv_array_pushf(&submodule_options, "--after-context=%d",
+				 opt->post_context);
+	if (opt->funcname)
+		argv_array_push(&submodule_options, "-p");
+	if (opt->funcbody)
+		argv_array_push(&submodule_options, "-W");
+	if (opt->all_match)
+		argv_array_push(&submodule_options, "--all-match");
+	if (opt->debug)
+		argv_array_push(&submodule_options, "--debug");
+	if (opt->status_only)
+		argv_array_push(&submodule_options, "-q");
+
+	switch (pattern_type_arg) {
+	case GREP_PATTERN_TYPE_BRE:
+		argv_array_push(&submodule_options, "-G");
+		break;
+	case GREP_PATTERN_TYPE_ERE:
+		argv_array_push(&submodule_options, "-E");
+		break;
+	case GREP_PATTERN_TYPE_FIXED:
+		argv_array_push(&submodule_options, "-F");
+		break;
+	case GREP_PATTERN_TYPE_PCRE:
+		argv_array_push(&submodule_options, "-P");
+		break;
+	case GREP_PATTERN_TYPE_UNSPECIFIED:
+		break;
+	}
+
+	for (pattern = opt->pattern_list; pattern != NULL;
+	     pattern = pattern->next) {
+		switch (pattern->token) {
+		case GREP_PATTERN:
+			argv_array_pushf(&submodule_options, "-e%s",
+					 pattern->pattern);
+			break;
+		case GREP_AND:
+		case GREP_OPEN_PAREN:
+		case GREP_CLOSE_PAREN:
+		case GREP_NOT:
+		case GREP_OR:
+			argv_array_push(&submodule_options, pattern->pattern);
+			break;
+		/* BODY and HEAD are not used by git-grep */
+		case GREP_PATTERN_BODY:
+		case GREP_PATTERN_HEAD:
+			break;
+		}
+	}
+
+	/*
+	 * Limit number of threads for child process to use.
+	 * This is to prevent potential fork-bomb behavior of git-grep as each
+	 * submodule process has its own thread pool.
+	 */
+	argv_array_pushf(&submodule_options, "--threads=%d",
+			 (num_threads + 1) / 2);
+
+	/* Add Pathspecs */
+	argv_array_push(&submodule_options, "--");
+	for (i = 0; i < pathspec->nr; i++)
+		argv_array_push(&submodule_options,
+				pathspec->items[i].original);
+}
+
+/*
+ * Launch child process to grep contents of a submodule
+ */
+static int grep_submodule_launch(struct grep_opt *opt,
+				 const struct grep_source *gs)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+	int status, i;
+	const char *end_of_base;
+	const char *name;
+	struct work_item *w = opt->output_priv;
+
+	end_of_base = strchr(gs->name, ':');
+	if (gs->identifier && end_of_base)
+		name = end_of_base + 1;
+	else
+		name = gs->name;
+
+	prepare_submodule_repo_env(&cp.env_array);
+	argv_array_push(&cp.env_array, GIT_DIR_ENVIRONMENT);
+
+	/* Add super prefix */
+	argv_array_pushf(&cp.args, "--super-prefix=%s%s/",
+			 super_prefix ? super_prefix : "",
+			 name);
+	argv_array_push(&cp.args, "grep");
+
+	/*
+	 * Add basename of parent project
+	 * When performing grep on a tree object the filename is prefixed
+	 * with the object's name: 'tree-name:filename'.  In order to
+	 * provide uniformity of output we want to pass the name of the
+	 * parent project's object name to the submodule so the submodule can
+	 * prefix its output with the parent's name and not its own SHA1.
+	 */
+	if (gs->identifier && end_of_base)
+		argv_array_pushf(&cp.args, "--parent-basename=%.*s",
+				 (int) (end_of_base - gs->name),
+				 gs->name);
+
+	/* Add options */
+	for (i = 0; i < submodule_options.argc; i++) {
+		/*
+		 * If there is a tree identifier for the submodule, add the
+		 * rev after adding the submodule options but before the
+		 * pathspecs.  To do this we listen for the '--' and insert the
+		 * sha1 before pushing the '--' onto the child process argv
+		 * array.
+		 */
+		if (gs->identifier &&
+		    !strcmp("--", submodule_options.argv[i])) {
+			argv_array_push(&cp.args, sha1_to_hex(gs->identifier));
+		}
+
+		argv_array_push(&cp.args, submodule_options.argv[i]);
+	}
+
+	cp.git_cmd = 1;
+	cp.dir = gs->path;
+
+	/*
+	 * Capture output to output buffer and check the return code from the
+	 * child process.  A '0' indicates a hit, a '1' indicates no hit and
+	 * anything else is an error.
+	 */
+	status = capture_command(&cp, &w->out, 0);
+	if (status && (status != 1)) {
+		/* flush the buffer */
+		write_or_die(1, w->out.buf, w->out.len);
+		die("process for submodule '%s' failed with exit code: %d",
+		    gs->name, status);
+	}
+
+	/* invert the return code to make a hit equal to 1 */
+	return !status;
+}
+
+/*
+ * Prep grep structures for a submodule grep
+ * sha1: the sha1 of the submodule or NULL if using the working tree
+ * filename: name of the submodule including tree name of parent
+ * path: location of the submodule
+ */
+static int grep_submodule(struct grep_opt *opt, const unsigned char *sha1,
+			  const char *filename, const char *path)
+{
+	if (!is_submodule_initialized(path))
+		return 0;
+	if (!is_submodule_populated(path)) {
+		/*
+		 * If searching history, check for the presense of the
+		 * submodule's gitdir before skipping the submodule.
+		 */
+		if (sha1) {
+			const struct submodule *sub =
+					submodule_from_path(null_sha1, path);
+			if (sub)
+				path = git_path("modules/%s", sub->name);
+
+			if (!(is_directory(path) && is_git_directory(path)))
+				return 0;
+		} else {
+			return 0;
+		}
+	}
+
+#ifndef NO_PTHREADS
+	if (num_threads) {
+		add_work(opt, GREP_SOURCE_SUBMODULE, filename, path, sha1);
+		return 0;
+	} else
+#endif
+	{
+		struct work_item w;
+		int hit;
+
+		grep_source_init(&w.source, GREP_SOURCE_SUBMODULE,
+				 filename, path, sha1);
+		strbuf_init(&w.out, 0);
+		opt->output_priv = &w;
+		hit = grep_submodule_launch(opt, &w.source);
+
+		write_or_die(1, w.out.buf, w.out.len);
+
+		grep_source_clear(&w.source);
+		strbuf_release(&w.out);
+		return hit;
+	}
+}
+
+static int grep_cache(struct grep_opt *opt, const struct pathspec *pathspec,
+		      int cached)
 {
 	int hit = 0;
 	int nr;
+	struct strbuf name = STRBUF_INIT;
+	int name_base_len = 0;
+	if (super_prefix) {
+		name_base_len = strlen(super_prefix);
+		strbuf_addstr(&name, super_prefix);
+	}
+
 	read_cache();
 
 	for (nr = 0; nr < active_nr; nr++) {
 		const struct cache_entry *ce = active_cache[nr];
-		if (!S_ISREG(ce->ce_mode))
-			continue;
-		if (!ce_path_match(ce, pathspec, NULL))
+		strbuf_setlen(&name, name_base_len);
+		strbuf_addstr(&name, ce->name);
+
+		if (S_ISREG(ce->ce_mode) &&
+		    match_pathspec(pathspec, name.buf, name.len, 0, NULL,
+				   S_ISDIR(ce->ce_mode) ||
+				   S_ISGITLINK(ce->ce_mode))) {
+			/*
+			 * If CE_VALID is on, we assume worktree file and its
+			 * cache entry are identical, even if worktree file has
+			 * been modified, so use cache version instead
+			 */
+			if (cached || (ce->ce_flags & CE_VALID) ||
+			    ce_skip_worktree(ce)) {
+				if (ce_stage(ce) || ce_intent_to_add(ce))
+					continue;
+				hit |= grep_sha1(opt, ce->oid.hash, ce->name,
+						 0, ce->name);
+			} else {
+				hit |= grep_file(opt, ce->name);
+			}
+		} else if (recurse_submodules && S_ISGITLINK(ce->ce_mode) &&
+			   submodule_path_match(pathspec, name.buf, NULL)) {
+			hit |= grep_submodule(opt, NULL, ce->name, ce->name);
+		} else {
 			continue;
-		/*
-		 * If CE_VALID is on, we assume worktree file and its cache entry
-		 * are identical, even if worktree file has been modified, so use
-		 * cache version instead
-		 */
-		if (cached || (ce->ce_flags & CE_VALID) || ce_skip_worktree(ce)) {
-			if (ce_stage(ce) || ce_intent_to_add(ce))
-				continue;
-			hit |= grep_sha1(opt, ce->oid.hash, ce->name, 0,
-					 ce->name);
 		}
-		else
-			hit |= grep_file(opt, ce->name);
+
 		if (ce_stage(ce)) {
 			do {
 				nr++;
@@ -413,6 +712,8 @@ static int grep_cache(struct grep_opt *opt, const struct pathspec *pathspec, int
 		if (hit && opt->status_only)
 			break;
 	}
+
+	strbuf_release(&name);
 	return hit;
 }
 
@@ -424,12 +725,22 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 	enum interesting match = entry_not_interesting;
 	struct name_entry entry;
 	int old_baselen = base->len;
+	struct strbuf name = STRBUF_INIT;
+	int name_base_len = 0;
+	if (super_prefix) {
+		strbuf_addstr(&name, super_prefix);
+		name_base_len = name.len;
+	}
 
 	while (tree_entry(tree, &entry)) {
 		int te_len = tree_entry_len(&entry);
 
 		if (match != all_entries_interesting) {
-			match = tree_entry_interesting(&entry, base, tn_len, pathspec);
+			strbuf_addstr(&name, base->buf + tn_len);
+			match = tree_entry_interesting(&entry, &name,
+						       0, pathspec);
+			strbuf_setlen(&name, name_base_len);
+
 			if (match == all_entries_not_interesting)
 				break;
 			if (match == entry_not_interesting)
@@ -441,8 +752,7 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 		if (S_ISREG(entry.mode)) {
 			hit |= grep_sha1(opt, entry.oid->hash, base->buf, tn_len,
 					 check_attr ? base->buf + tn_len : NULL);
-		}
-		else if (S_ISDIR(entry.mode)) {
+		} else if (S_ISDIR(entry.mode)) {
 			enum object_type type;
 			struct tree_desc sub;
 			void *data;
@@ -458,12 +768,18 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 			hit |= grep_tree(opt, pathspec, &sub, base, tn_len,
 					 check_attr);
 			free(data);
+		} else if (recurse_submodules && S_ISGITLINK(entry.mode)) {
+			hit |= grep_submodule(opt, entry.oid->hash, base->buf,
+					      base->buf + tn_len);
 		}
+
 		strbuf_setlen(base, old_baselen);
 
 		if (hit && opt->status_only)
 			break;
 	}
+
+	strbuf_release(&name);
 	return hit;
 }
 
@@ -487,6 +803,10 @@ static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
 		if (!data)
 			die(_("unable to read tree (%s)"), oid_to_hex(&obj->oid));
 
+		/* Use parent's name as base when recursing submodules */
+		if (recurse_submodules && parent_basename)
+			name = parent_basename;
+
 		len = name ? strlen(name) : 0;
 		strbuf_init(&base, PATH_MAX + len + 1);
 		if (len) {
@@ -513,6 +833,12 @@ static int grep_objects(struct grep_opt *opt, const struct pathspec *pathspec,
 	for (i = 0; i < nr; i++) {
 		struct object *real_obj;
 		real_obj = deref_tag(list->objects[i].item, NULL, 0);
+
+		/* load the gitmodules file for this rev */
+		if (recurse_submodules) {
+			submodule_free();
+			gitmodules_config_sha1(real_obj->oid.hash);
+		}
 		if (grep_object(opt, pathspec, real_obj, list->objects[i].name, list->objects[i].path)) {
 			hit = 1;
 			if (opt->status_only)
@@ -651,6 +977,11 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			N_("search in both tracked and untracked files")),
 		OPT_SET_INT(0, "exclude-standard", &opt_exclude,
 			    N_("ignore files specified via '.gitignore'"), 1),
+		OPT_BOOL(0, "recurse-submodules", &recurse_submodules,
+			 N_("recursivley search in each submodule")),
+		OPT_STRING(0, "parent-basename", &parent_basename,
+			   N_("basename"),
+			   N_("prepend parent project's basename to output")),
 		OPT_GROUP(""),
 		OPT_BOOL('v', "invert-match", &opt.invert,
 			N_("show non-matching lines")),
@@ -755,6 +1086,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	init_grep_defaults();
 	git_config(grep_cmd_config, NULL);
 	grep_init(&opt, prefix);
+	super_prefix = get_super_prefix();
 
 	/*
 	 * If there is no -- then the paths must exist in the working
@@ -872,6 +1204,13 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	pathspec.max_depth = opt.max_depth;
 	pathspec.recursive = 1;
 
+	if (recurse_submodules) {
+		gitmodules_config();
+		compile_submodule_options(&opt, &pathspec, cached, untracked,
+					  opt_exclude, use_index,
+					  pattern_type_arg);
+	}
+
 	if (show_in_pager && (cached || list.nr))
 		die(_("--open-files-in-pager only works on the worktree"));
 
@@ -895,6 +1234,9 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		}
 	}
 
+	if (recurse_submodules && (!use_index || untracked))
+		die(_("option not supported with --recurse-submodules."));
+
 	if (!show_in_pager && !opt.status_only)
 		setup_pager();
 
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 2399b97d90..76d68fad00 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -338,7 +338,7 @@ int init_db(const char *git_dir, const char *real_git_dir,
 {
 	int reinit;
 	int exist_ok = flags & INIT_DB_EXIST_OK;
-	char *original_git_dir = xstrdup(real_path(git_dir));
+	char *original_git_dir = real_pathdup(git_dir);
 
 	if (real_git_dir) {
 		struct stat st;
@@ -489,7 +489,7 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, init_db_options, init_db_usage, 0);
 
 	if (real_git_dir && !is_absolute_path(real_git_dir))
-		real_git_dir = xstrdup(real_path(real_git_dir));
+		real_git_dir = real_pathdup(real_git_dir);
 
 	if (argc == 1) {
 		int mkdir_tried = 0;
@@ -560,7 +560,7 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 		const char *git_dir_parent = strrchr(git_dir, '/');
 		if (git_dir_parent) {
 			char *rel = xstrndup(git_dir, git_dir_parent - git_dir);
-			git_work_tree_cfg = xstrdup(real_path(rel));
+			git_work_tree_cfg = real_pathdup(rel);
 			free(rel);
 		}
 		if (!git_work_tree_cfg)
diff --git a/cache.h b/cache.h
index 1b67f078dd..c74df70127 100644
--- a/cache.h
+++ b/cache.h
@@ -1064,8 +1064,11 @@ static inline int is_absolute_path(const char *path)
 	return is_dir_sep(path[0]) || has_dos_drive_prefix(path);
 }
 int is_directory(const char *);
+char *strbuf_realpath(struct strbuf *resolved, const char *path,
+		      int die_on_error);
 const char *real_path(const char *path);
 const char *real_path_if_valid(const char *path);
+char *real_pathdup(const char *path);
 const char *absolute_path(const char *path);
 const char *remove_leading_path(const char *in, const char *prefix);
 const char *relative_path(const char *in, const char *prefix, struct strbuf *sb);
@@ -1691,6 +1694,8 @@ extern int git_default_config(const char *, const char *, void *);
 extern int git_config_from_file(config_fn_t fn, const char *, void *);
 extern int git_config_from_mem(config_fn_t fn, const enum config_origin_type,
 					const char *name, const char *buf, size_t len, void *data);
+extern int git_config_from_blob_sha1(config_fn_t fn, const char *name,
+				     const unsigned char *sha1, void *data);
 extern void git_config_push_parameter(const char *text);
 extern int git_config_from_parameters(config_fn_t fn, void *data);
 extern void git_config(config_fn_t fn, void *);
diff --git a/config.c b/config.c
index 617b2e3cf4..b680f79732 100644
--- a/config.c
+++ b/config.c
@@ -1236,10 +1236,10 @@ int git_config_from_mem(config_fn_t fn, const enum config_origin_type origin_typ
 	return do_config_from(&top, fn, data);
 }
 
-static int git_config_from_blob_sha1(config_fn_t fn,
-				     const char *name,
-				     const unsigned char *sha1,
-				     void *data)
+int git_config_from_blob_sha1(config_fn_t fn,
+			      const char *name,
+			      const unsigned char *sha1,
+			      void *data)
 {
 	enum object_type type;
 	char *buf;
diff --git a/environment.c b/environment.c
index 4bce3eebfa..8a83101d04 100644
--- a/environment.c
+++ b/environment.c
@@ -259,7 +259,7 @@ void set_git_work_tree(const char *new_work_tree)
 		return;
 	}
 	git_work_tree_initialized = 1;
-	work_tree = xstrdup(real_path(new_work_tree));
+	work_tree = real_pathdup(new_work_tree);
 }
 
 const char *get_git_work_tree(void)
diff --git a/git.c b/git.c
index bbaa949e9c..e4714aadb3 100644
--- a/git.c
+++ b/git.c
@@ -434,7 +434,7 @@ static struct cmd_struct commands[] = {
 	{ "fsck-objects", cmd_fsck, RUN_SETUP },
 	{ "gc", cmd_gc, RUN_SETUP },
 	{ "get-tar-commit-id", cmd_get_tar_commit_id },
-	{ "grep", cmd_grep, RUN_SETUP_GENTLY },
+	{ "grep", cmd_grep, RUN_SETUP_GENTLY | SUPPORT_SUPER_PREFIX },
 	{ "hash-object", cmd_hash_object },
 	{ "help", cmd_help },
 	{ "index-pack", cmd_index_pack, RUN_SETUP_GENTLY },
diff --git a/grep.c b/grep.c
index 1194d35b5d..0dbdc1d007 100644
--- a/grep.c
+++ b/grep.c
@@ -1735,12 +1735,23 @@ void grep_source_init(struct grep_source *gs, enum grep_source_type type,
 	case GREP_SOURCE_FILE:
 		gs->identifier = xstrdup(identifier);
 		break;
+	case GREP_SOURCE_SUBMODULE:
+		if (!identifier) {
+			gs->identifier = NULL;
+			break;
+		}
+		/*
+		 * FALL THROUGH
+		 * If the identifier is non-NULL (in the submodule case) it
+		 * will be a SHA1 that needs to be copied.
+		 */
 	case GREP_SOURCE_SHA1:
 		gs->identifier = xmalloc(20);
 		hashcpy(gs->identifier, identifier);
 		break;
 	case GREP_SOURCE_BUF:
 		gs->identifier = NULL;
+		break;
 	}
 }
 
@@ -1760,6 +1771,7 @@ void grep_source_clear_data(struct grep_source *gs)
 	switch (gs->type) {
 	case GREP_SOURCE_FILE:
 	case GREP_SOURCE_SHA1:
+	case GREP_SOURCE_SUBMODULE:
 		free(gs->buf);
 		gs->buf = NULL;
 		gs->size = 0;
@@ -1831,8 +1843,10 @@ static int grep_source_load(struct grep_source *gs)
 		return grep_source_load_sha1(gs);
 	case GREP_SOURCE_BUF:
 		return gs->buf ? 0 : -1;
+	case GREP_SOURCE_SUBMODULE:
+		break;
 	}
-	die("BUG: invalid grep_source type");
+	die("BUG: invalid grep_source type to load");
 }
 
 void grep_source_load_driver(struct grep_source *gs)
diff --git a/grep.h b/grep.h
index 5856a23e46..267534ca24 100644
--- a/grep.h
+++ b/grep.h
@@ -161,6 +161,7 @@ struct grep_source {
 		GREP_SOURCE_SHA1,
 		GREP_SOURCE_FILE,
 		GREP_SOURCE_BUF,
+		GREP_SOURCE_SUBMODULE,
 	} type;
 	void *identifier;
 
diff --git a/setup.c b/setup.c
index fe572b82c3..1b534a7508 100644
--- a/setup.c
+++ b/setup.c
@@ -256,8 +256,10 @@ int get_common_dir_noenv(struct strbuf *sb, const char *gitdir)
 		strbuf_addbuf(&path, &data);
 		strbuf_addstr(sb, real_path(path.buf));
 		ret = 1;
-	} else
+	} else {
 		strbuf_addstr(sb, gitdir);
+	}
+
 	strbuf_release(&data);
 	strbuf_release(&path);
 	return ret;
@@ -692,7 +694,7 @@ static const char *setup_discovered_git_dir(const char *gitdir,
 	/* --work-tree is set without --git-dir; use discovered one */
 	if (getenv(GIT_WORK_TREE_ENVIRONMENT) || git_work_tree_cfg) {
 		if (offset != cwd->len && !is_absolute_path(gitdir))
-			gitdir = xstrdup(real_path(gitdir));
+			gitdir = real_pathdup(gitdir);
 		if (chdir(cwd->buf))
 			die_errno("Could not come back to cwd");
 		return setup_explicit_git_dir(gitdir, cwd, nongit_ok);
@@ -800,11 +802,12 @@ static int canonicalize_ceiling_entry(struct string_list_item *item,
 		/* Keep entry but do not canonicalize it */
 		return 1;
 	} else {
-		const char *real_path = real_path_if_valid(ceil);
-		if (!real_path)
+		char *real_path = real_pathdup(ceil);
+		if (!real_path) {
 			return 0;
+		}
 		free(item->string);
-		item->string = xstrdup(real_path);
+		item->string = real_path;
 		return 1;
 	}
 }
diff --git a/sha1_file.c b/sha1_file.c
index 1eb47f6113..b5e827ac9e 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -284,7 +284,7 @@ static int link_alt_odb_entry(const char *entry, const char *relative_base,
 	struct strbuf pathbuf = STRBUF_INIT;
 
 	if (!is_absolute_path(entry) && relative_base) {
-		strbuf_addstr(&pathbuf, real_path(relative_base));
+		strbuf_realpath(&pathbuf, relative_base, 1);
 		strbuf_addch(&pathbuf, '/');
 	}
 	strbuf_addstr(&pathbuf, entry);
diff --git a/submodule-config.c b/submodule-config.c
index ec13ab5a3d..4bf50f398a 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -379,7 +379,7 @@ static int parse_config(const char *var, const char *value, void *data)
 	return ret;
 }
 
-static int gitmodule_sha1_from_commit(const unsigned char *treeish_name,
+int gitmodule_sha1_from_commit(const unsigned char *treeish_name,
 				      unsigned char *gitmodules_sha1,
 				      struct strbuf *rev)
 {
diff --git a/submodule-config.h b/submodule-config.h
index 99df8e593c..70f19363fd 100644
--- a/submodule-config.h
+++ b/submodule-config.h
@@ -29,6 +29,9 @@ const struct submodule *submodule_from_name(const unsigned char *commit_or_tree,
 		const char *name);
 const struct submodule *submodule_from_path(const unsigned char *commit_or_tree,
 		const char *path);
+extern int gitmodule_sha1_from_commit(const unsigned char *commit_sha1,
+				      unsigned char *gitmodules_sha1,
+				      struct strbuf *rev);
 void submodule_free(void);
 
 #endif /* SUBMODULE_CONFIG_H */
diff --git a/submodule.c b/submodule.c
index 73521cdbb2..f8fee3dfdd 100644
--- a/submodule.c
+++ b/submodule.c
@@ -199,6 +199,56 @@ void gitmodules_config(void)
 	}
 }
 
+void gitmodules_config_sha1(const unsigned char *commit_sha1)
+{
+	struct strbuf rev = STRBUF_INIT;
+	unsigned char sha1[20];
+
+	if (gitmodule_sha1_from_commit(commit_sha1, sha1, &rev)) {
+		git_config_from_blob_sha1(submodule_config, rev.buf,
+					  sha1, NULL);
+	}
+	strbuf_release(&rev);
+}
+
+/*
+ * Determine if a submodule has been initialized at a given 'path'
+ */
+int is_submodule_initialized(const char *path)
+{
+	int ret = 0;
+	const struct submodule *module = NULL;
+
+	module = submodule_from_path(null_sha1, path);
+
+	if (module) {
+		char *key = xstrfmt("submodule.%s.url", module->name);
+		char *value = NULL;
+
+		ret = !git_config_get_string(key, &value);
+
+		free(value);
+		free(key);
+	}
+
+	return ret;
+}
+
+/*
+ * Determine if a submodule has been populated at a given 'path'
+ */
+int is_submodule_populated(const char *path)
+{
+	int ret = 0;
+	char *gitdir = xstrfmt("%s/.git", path);
+
+	if (resolve_gitdir(gitdir))
+		ret = 1;
+
+	free(gitdir);
+	return ret;
+}
+
 int parse_submodule_update_strategy(const char *value,
 		struct submodule_update_strategy *dst)
 {
@@ -1333,7 +1383,7 @@ static void relocate_single_git_dir_into_superproject(const char *prefix,
 		/* If it is an actual gitfile, it doesn't need migration. */
 		return;
 
-	real_old_git_dir = xstrdup(real_path(old_git_dir));
+	real_old_git_dir = real_pathdup(old_git_dir);
 
 	sub = submodule_from_path(null_sha1, path);
 	if (!sub)
@@ -1342,7 +1392,7 @@ static void relocate_single_git_dir_into_superproject(const char *prefix,
 	new_git_dir = git_path("modules/%s", sub->name);
 	if (safe_create_leading_directories_const(new_git_dir) < 0)
 		die(_("could not create directory '%s'"), new_git_dir);
-	real_new_git_dir = xstrdup(real_path(new_git_dir));
+	real_new_git_dir = real_pathdup(new_git_dir);
 
 	if (!prefix)
 		prefix = get_super_prefix();
@@ -1379,8 +1429,8 @@ void absorb_git_dir_into_superproject(const char *prefix,
 		goto out;
 
 	/* Is it already absorbed into the superprojects git dir? */
-	real_sub_git_dir = xstrdup(real_path(sub_git_dir));
-	real_common_git_dir = xstrdup(real_path(get_git_common_dir()));
+	real_sub_git_dir = real_pathdup(sub_git_dir);
+	real_common_git_dir = real_pathdup(get_git_common_dir());
 	if (!skip_prefix(real_sub_git_dir, real_common_git_dir, &v))
 		relocate_single_git_dir_into_superproject(prefix, path);
 
diff --git a/submodule.h b/submodule.h
index b7576d6f43..1ccaf0e6ba 100644
--- a/submodule.h
+++ b/submodule.h
@@ -38,6 +38,9 @@ void set_diffopt_flags_from_submodule_config(struct diff_options *diffopt,
 		const char *path);
 int submodule_config(const char *var, const char *value, void *cb);
 void gitmodules_config(void);
+extern void gitmodules_config_sha1(const unsigned char *commit_sha1);
+extern int is_submodule_initialized(const char *path);
+extern int is_submodule_populated(const char *path);
 int parse_submodule_update_strategy(const char *value,
 		struct submodule_update_strategy *dst);
 const char *submodule_strategy_to_string(const struct submodule_update_strategy *s);
diff --git a/t/t7814-grep-recurse-submodules.sh b/t/t7814-grep-recurse-submodules.sh
new file mode 100755
index 0000000000..67247a01d6
--- /dev/null
+++ b/t/t7814-grep-recurse-submodules.sh
@@ -0,0 +1,241 @@
+#!/bin/sh
+
+test_description='Test grep recurse-submodules feature
+
+This test verifies the recurse-submodules feature correctly greps across
+submodules.
+'
+
+. ./test-lib.sh
+
+test_expect_success 'setup directory structure and submodule' '
+	echo "foobar" >a &&
+	mkdir b &&
+	echo "bar" >b/b &&
+	git add a b &&
+	git commit -m "add a and b" &&
+	git init submodule &&
+	echo "foobar" >submodule/a &&
+	git -C submodule add a &&
+	git -C submodule commit -m "add a" &&
+	git submodule add ./submodule &&
+	git commit -m "added submodule"
+'
+
+test_expect_success 'grep correctly finds patterns in a submodule' '
+	cat >expect <<-\EOF &&
+	a:foobar
+	b/b:bar
+	submodule/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep and basic pathspecs' '
+	cat >expect <<-\EOF &&
+	submodule/a:foobar
+	EOF
+
+	git grep -e. --recurse-submodules -- submodule >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep and nested submodules' '
+	git init submodule/sub &&
+	echo "foobar" >submodule/sub/a &&
+	git -C submodule/sub add a &&
+	git -C submodule/sub commit -m "add a" &&
+	git -C submodule submodule add ./sub &&
+	git -C submodule add sub &&
+	git -C submodule commit -m "added sub" &&
+	git add submodule &&
+	git commit -m "updated submodule" &&
+
+	cat >expect <<-\EOF &&
+	a:foobar
+	b/b:bar
+	submodule/a:foobar
+	submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep and multiple patterns' '
+	cat >expect <<-\EOF &&
+	a:foobar
+	submodule/a:foobar
+	submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --and -e "foo" --recurse-submodules >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep and multiple patterns' '
+	cat >expect <<-\EOF &&
+	b/b:bar
+	EOF
+
+	git grep -e "bar" --and --not -e "foo" --recurse-submodules >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'basic grep tree' '
+	cat >expect <<-\EOF &&
+	HEAD:a:foobar
+	HEAD:b/b:bar
+	HEAD:submodule/a:foobar
+	HEAD:submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree HEAD^' '
+	cat >expect <<-\EOF &&
+	HEAD^:a:foobar
+	HEAD^:b/b:bar
+	HEAD^:submodule/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD^ >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree HEAD^^' '
+	cat >expect <<-\EOF &&
+	HEAD^^:a:foobar
+	HEAD^^:b/b:bar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD^^ >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree and pathspecs' '
+	cat >expect <<-\EOF &&
+	HEAD:submodule/a:foobar
+	HEAD:submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD -- submodule >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree and pathspecs' '
+	cat >expect <<-\EOF &&
+	HEAD:submodule/a:foobar
+	HEAD:submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD -- "submodule*a" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree and more pathspecs' '
+	cat >expect <<-\EOF &&
+	HEAD:submodule/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD -- "submodul?/a" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep tree and more pathspecs' '
+	cat >expect <<-\EOF &&
+	HEAD:submodule/sub/a:foobar
+	EOF
+
+	git grep -e "bar" --recurse-submodules HEAD -- "submodul*/sub/a" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success !MINGW 'grep recurse submodule colon in name' '
+	git init parent &&
+	test_when_finished "rm -rf parent" &&
+	echo "foobar" >"parent/fi:le" &&
+	git -C parent add "fi:le" &&
+	git -C parent commit -m "add fi:le" &&
+
+	git init "su:b" &&
+	test_when_finished "rm -rf su:b" &&
+	echo "foobar" >"su:b/fi:le" &&
+	git -C "su:b" add "fi:le" &&
+	git -C "su:b" commit -m "add fi:le" &&
+
+	git -C parent submodule add "../su:b" "su:b" &&
+	git -C parent commit -m "add submodule" &&
+
+	cat >expect <<-\EOF &&
+	fi:le:foobar
+	su:b/fi:le:foobar
+	EOF
+	git -C parent grep -e "foobar" --recurse-submodules >actual &&
+	test_cmp expect actual &&
+
+	cat >expect <<-\EOF &&
+	HEAD:fi:le:foobar
+	HEAD:su:b/fi:le:foobar
+	EOF
+	git -C parent grep -e "foobar" --recurse-submodules HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep history with moved submoules' '
+	git init parent &&
+	test_when_finished "rm -rf parent" &&
+	echo "foobar" >parent/file &&
+	git -C parent add file &&
+	git -C parent commit -m "add file" &&
+
+	git init sub &&
+	test_when_finished "rm -rf sub" &&
+	echo "foobar" >sub/file &&
+	git -C sub add file &&
+	git -C sub commit -m "add file" &&
+
+	git -C parent submodule add ../sub dir/sub &&
+	git -C parent commit -m "add submodule" &&
+
+	cat >expect <<-\EOF &&
+	dir/sub/file:foobar
+	file:foobar
+	EOF
+	git -C parent grep -e "foobar" --recurse-submodules >actual &&
+	test_cmp expect actual &&
+
+	git -C parent mv dir/sub sub-moved &&
+	git -C parent commit -m "moved submodule" &&
+
+	cat >expect <<-\EOF &&
+	file:foobar
+	sub-moved/file:foobar
+	EOF
+	git -C parent grep -e "foobar" --recurse-submodules >actual &&
+	test_cmp expect actual &&
+
+	cat >expect <<-\EOF &&
+	HEAD^:dir/sub/file:foobar
+	HEAD^:file:foobar
+	EOF
+	git -C parent grep -e "foobar" --recurse-submodules HEAD^ >actual &&
+	test_cmp expect actual
+'
+
+test_incompatible_with_recurse_submodules ()
+{
+	test_expect_success "--recurse-submodules and $1 are incompatible" "
+		test_must_fail git grep -e. --recurse-submodules $1 2>actual &&
+		test_i18ngrep 'not supported with --recurse-submodules' actual
+	"
+}
+
+test_incompatible_with_recurse_submodules --untracked
+test_incompatible_with_recurse_submodules --no-index
+
+test_done
diff --git a/transport.c b/transport.c
index 3e8799a611..c86ba2eb89 100644
--- a/transport.c
+++ b/transport.c
@@ -1214,7 +1214,7 @@ static int refs_from_alternate_cb(struct alternate_object_database *e,
 	const struct ref *extra;
 	struct alternate_refs_data *cb = data;
 
-	other = xstrdup(real_path(e->path));
+	other = real_pathdup(e->path);
 	len = strlen(other);
 
 	while (other[len-1] == '/')
diff --git a/tree-walk.c b/tree-walk.c
index 828f4356be..ff77605680 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -1004,6 +1004,19 @@ static enum interesting do_match(const struct name_entry *entry,
 				 */
 				if (ps->recursive && S_ISDIR(entry->mode))
 					return entry_interesting;
+
+				/*
+				 * When matching against submodules with
+				 * wildcard characters, ensure that the entry
+				 * at least matches up to the first wild
+				 * character.  More accurate matching can then
+				 * be performed in the submodule itself.
+				 */
+				if (ps->recursive && S_ISGITLINK(entry->mode) &&
+				    !ps_strncmp(item, match + baselen,
+						entry->path,
+						item->nowildcard_len - baselen))
+					return entry_interesting;
 			}
 
 			continue;
@@ -1040,6 +1053,21 @@ match_wildcards:
 			strbuf_setlen(base, base_offset + baselen);
 			return entry_interesting;
 		}
+
+		/*
+		 * When matching against submodules with
+		 * wildcard characters, ensure that the entry
+		 * at least matches up to the first wild
+		 * character.  More accurate matching can then
+		 * be performed in the submodule itself.
+		 */
+		if (ps->recursive && S_ISGITLINK(entry->mode) &&
+		    !ps_strncmp(item, match, base->buf + base_offset,
+				item->nowildcard_len)) {
+			strbuf_setlen(base, base_offset + baselen);
+			return entry_interesting;
+		}
+
 		strbuf_setlen(base, base_offset + baselen);
 
 		/*
diff --git a/worktree.c b/worktree.c
index 828fd7a0ad..53b4771c04 100644
--- a/worktree.c
+++ b/worktree.c
@@ -255,7 +255,7 @@ struct worktree *find_worktree(struct worktree **list,
 		return wt;
 
 	arg = prefix_filename(prefix, strlen(prefix), arg);
-	path = xstrdup(real_path(arg));
+	path = real_pathdup(arg);
 	for (; *list; list++)
 		if (!fspathcmp(path, real_path((*list)->path)))
 			break;