git-apply: apply submodule changes

Apply "Subproject commit HEX" changes produced by git-diff.
As usual in the current git, only the superproject itself is actually
modified (possibly creating empty directories for new submodules).
Any checked-out submodule is left untouched and is not required to
be up-to-date.

With clean-ups from Junio C Hamano.

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 117 insertions, 25 deletions

diff --git a/Documentation/git-apply.txt b/Documentation/git-apply.txt
index f03f66165..4c7e3a2f7 100644
--- a/Documentation/git-apply.txt
+++ b/Documentation/git-apply.txt
@@ -171,6 +171,20 @@ apply.whitespace::
 	When no `--whitespace` flag is given from the command
 	line, this configuration item is used as the default.
 
+Submodules
+----------
+If the patch contains any changes to submodules then gitlink:git-apply[1]
+treats these changes as follows.
+
+If --index is specified (explicitly or implicitly), then the submodule
+commits must match the index exactly for the patch to apply.  If any
+of the submodules are checked-out, then these check-outs are completely
+ignored, i.e., they are not required to be up-to-date or clean and they
+are not updated.
+
+If --index is not specified, then the submodule commits in the patch
+are ignored and only the absence of presence of the corresponding
+subdirectory is checked and (if possible) updated.
 
 Author
 ------
diff --git a/builtin-apply.c b/builtin-apply.c
index da270755a..25b144790 100644
--- a/builtin-apply.c
+++ b/builtin-apply.c
@@ -1984,6 +1984,25 @@ static int apply_fragments(struct buffer_desc *desc, struct patch *patch)
 	return 0;
 }
 
+static int read_file_or_gitlink(struct cache_entry *ce, char **buf_p,
+				unsigned long *size_p)
+{
+	if (!ce)
+		return 0;
+
+	if (S_ISGITLINK(ntohl(ce->ce_mode))) {
+		*buf_p = xmalloc(100);
+		*size_p = snprintf(*buf_p, 100,
+			"Subproject commit %s\n", sha1_to_hex(ce->sha1));
+	} else {
+		enum object_type type;
+		*buf_p = read_sha1_file(ce->sha1, &type, size_p);
+		if (!*buf_p)
+			return -1;
+	}
+	return 0;
+}
+
 static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
 	char *buf;
@@ -1994,22 +2013,32 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	alloc = 0;
 	buf = NULL;
 	if (cached) {
-		if (ce) {
-			enum object_type type;
-			buf = read_sha1_file(ce->sha1, &type, &size);
-			if (!buf)
+		if (read_file_or_gitlink(ce, &buf, &size))
+			return error("read of %s failed", patch->old_name);
+		alloc = size;
+	} else if (patch->old_name) {
+		if (S_ISGITLINK(patch->old_mode)) {
+			if (ce)
+				read_file_or_gitlink(ce, &buf, &size);
+			else {
+				/*
+				 * There is no way to apply subproject
+				 * patch without looking at the index.
+				 */
+				patch->fragments = NULL;
+				size = 0;
+			}
+		}
+		else {
+			size = xsize_t(st->st_size);
+			alloc = size + 8192;
+			buf = xmalloc(alloc);
+			if (read_old_data(st, patch->old_name,
+					  &buf, &alloc, &size))
 				return error("read of %s failed",
 					     patch->old_name);
-			alloc = size;
 		}
 	}
-	else if (patch->old_name) {
-		size = xsize_t(st->st_size);
-		alloc = size + 8192;
-		buf = xmalloc(alloc);
-		if (read_old_data(st, patch->old_name, &buf, &alloc, &size))
-			return error("read of %s failed", patch->old_name);
-	}
 
 	desc.size = size;
 	desc.alloc = alloc;
@@ -2055,6 +2084,16 @@ static int check_to_create_blob(const char *new_name, int ok_if_exists)
 	return 0;
 }
 
+static int verify_index_match(struct cache_entry *ce, struct stat *st)
+{
+	if (S_ISGITLINK(ntohl(ce->ce_mode))) {
+		if (!S_ISDIR(st->st_mode))
+			return -1;
+		return 0;
+	}
+	return ce_match_stat(ce, st, 1);
+}
+
 static int check_patch(struct patch *patch, struct patch *prev_patch)
 {
 	struct stat st;
@@ -2065,8 +2104,14 @@ static int check_patch(struct patch *patch, struct patch *prev_patch)
 	int ok_if_exists;
 
 	patch->rejected = 1; /* we will drop this after we succeed */
+
+	/*
+	 * Make sure that we do not have local modifications from the
+	 * index when we are looking at the index.  Also make sure
+	 * we have the preimage file to be patched in the work tree,
+	 * unless --cached, which tells git to apply only in the index.
+	 */
 	if (old_name) {
-		int changed = 0;
 		int stat_ret = 0;
 		unsigned st_mode = 0;
 
@@ -2096,15 +2141,12 @@ static int check_patch(struct patch *patch, struct patch *prev_patch)
 				    lstat(old_name, &st))
 					return -1;
 			}
-			if (!cached)
-				changed = ce_match_stat(ce, &st, 1);
-			if (changed)
+			if (!cached && verify_index_match(ce, &st))
 				return error("%s: does not match index",
 					     old_name);
 			if (cached)
 				st_mode = ntohl(ce->ce_mode);
-		}
-		else if (stat_ret < 0)
+		} else if (stat_ret < 0)
 			return error("%s: %s", old_name, strerror(errno));
 
 		if (!cached)
@@ -2354,7 +2396,11 @@ static void remove_file(struct patch *patch, int rmdir_empty)
 		cache_tree_invalidate_path(active_cache_tree, patch->old_name);
 	}
 	if (!cached) {
-		if (!unlink(patch->old_name) && rmdir_empty) {
+		if (S_ISGITLINK(patch->old_mode)) {
+			if (rmdir(patch->old_name))
+				warning("unable to remove submodule %s",
+					patch->old_name);
+		} else if (!unlink(patch->old_name) && rmdir_empty) {
 			char *name = xstrdup(patch->old_name);
 			char *end = strrchr(name, '/');
 			while (end) {
@@ -2382,13 +2428,21 @@ static void add_index_file(const char *path, unsigned mode, void *buf, unsigned
 	memcpy(ce->name, path, namelen);
 	ce->ce_mode = create_ce_mode(mode);
 	ce->ce_flags = htons(namelen);
-	if (!cached) {
-		if (lstat(path, &st) < 0)
-			die("unable to stat newly created file %s", path);
-		fill_stat_cache_info(ce, &st);
+	if (S_ISGITLINK(mode)) {
+		const char *s = buf;
+
+		if (get_sha1_hex(s + strlen("Subproject commit "), ce->sha1))
+			die("corrupt patch for subproject %s", path);
+	} else {
+		if (!cached) {
+			if (lstat(path, &st) < 0)
+				die("unable to stat newly created file %s",
+				    path);
+			fill_stat_cache_info(ce, &st);
+		}
+		if (write_sha1_file(buf, size, blob_type, ce->sha1) < 0)
+			die("unable to create backing store for newly created file %s", path);
 	}
-	if (write_sha1_file(buf, size, blob_type, ce->sha1) < 0)
-		die("unable to create backing store for newly created file %s", path);
 	if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
 		die("unable to add cache entry for %s", path);
 }
@@ -2398,6 +2452,13 @@ static int try_create_file(const char *path, unsigned int mode, const char *buf,
 	int fd;
 	char *nbuf;
 
+	if (S_ISGITLINK(mode)) {
+		struct stat st;
+		if (!lstat(path, &st) && S_ISDIR(st.st_mode))
+			return 0;
+		return mkdir(path, 0777);
+	}
+
 	if (has_symlinks && S_ISLNK(mode))
 		/* Although buf:size is counted string, it also is NUL
 		 * terminated.
diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index e8ce7cdb8..9d142ed64 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh
@@ -175,4 +175,21 @@ test_expect_success 'checkout superproject with subproject already present' '
 	git-checkout master
 '
 
+test_expect_success 'apply submodule diff' '
+	git branch second &&
+	(
+		cd lib &&
+		echo s >s &&
+		git add s &&
+		git commit -m "change subproject"
+	) &&
+	git update-index --add lib &&
+	git-commit -m "change lib" &&
+	git-format-patch -1 --stdout >P.diff &&
+	git checkout second &&
+	git apply --index P.diff &&
+	D=$(git diff --cached master) &&
+	test -z "$D"
+'
+
 test_done