Do not take mode bits from index after type change.

When we do not trust executable bit from lstat(2), we copied
existing ce_mode bits without checking if the filesystem object
is a regular file (which is the only thing we apply the "trust
executable bit" business) nor if the blob in the index is a
regular file (otherwise, we should do the same as registering a
new regular file, which is to default non-executable).

Noticed by Johannes Sixt.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-apply.c

@@ -1988,7 +1988,7 @@ static int check_patch(struct patch *patch, struct patch *prev_patch)
 			return error("%s: %s", old_name, strerror(errno));
 
 		if (!cached)
-			st_mode = ntohl(create_ce_mode(st.st_mode));
+			st_mode = ntohl(ce_mode_from_stat(ce, st.st_mode));
 
 		if (patch->is_new < 0)
 			patch->is_new = 0;

builtin-update-index.c

@@ -109,16 +109,17 @@ static int add_file_to_cache(const char *path)
 	ce->ce_flags = htons(namelen);
 	fill_stat_cache_info(ce, &st);
 
-	ce->ce_mode = create_ce_mode(st.st_mode);
-	if (!trust_executable_bit) {
+	if (trust_executable_bit)
+		ce->ce_mode = create_ce_mode(st.st_mode);
+	else {
 		/* If there is an existing entry, pick the mode bits
 		 * from it, otherwise assume unexecutable.
 		 */
+		struct cache_entry *ent;
 		int pos = cache_name_pos(path, namelen);
-		if (0 <= pos)
-			ce->ce_mode = active_cache[pos]->ce_mode;
-		else if (S_ISREG(st.st_mode))
-			ce->ce_mode = create_ce_mode(S_IFREG | 0666);
+
+		ent = (0 <= pos) ? active_cache[pos] : NULL;
+		ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
 	}
 
 	if (index_path(ce->sha1, path, &st, !info_only))

cache.h

@@ -106,6 +106,16 @@ static inline unsigned int create_ce_mode(unsigned int mode)
 		return htonl(S_IFLNK);
 	return htonl(S_IFREG | ce_permissions(mode));
 }
+static inline unsigned int ce_mode_from_stat(struct cache_entry *ce, unsigned int mode)
+{
+	extern int trust_executable_bit;
+	if (!trust_executable_bit && S_ISREG(mode)) {
+		if (ce && S_ISREG(ntohl(ce->ce_mode)))
+			return ce->ce_mode;
+		return create_ce_mode(0666);
+	}
+	return create_ce_mode(mode);
+}
 #define canon_mode(mode) \
 	(S_ISREG(mode) ? (S_IFREG | ce_permissions(mode)) : \
 	S_ISLNK(mode) ? S_IFLNK : S_IFDIR)

diff-lib.c

@@ -170,9 +170,7 @@ static int get_stat_data(struct cache_entry *ce,
 		}
 		changed = ce_match_stat(ce, &st, 0);
 		if (changed) {
-			mode = create_ce_mode(st.st_mode);
-			if (!trust_executable_bit && S_ISREG(st.st_mode))
-				mode = ce->ce_mode;
+			mode = ce_mode_from_stat(ce, st.st_mode);
 			sha1 = no_sha1;
 		}
 	}

read-cache.c

@@ -344,16 +344,17 @@ int add_file_to_index(const char *path, int verbose)
 	ce->ce_flags = htons(namelen);
 	fill_stat_cache_info(ce, &st);
 
-	ce->ce_mode = create_ce_mode(st.st_mode);
-	if (!trust_executable_bit) {
+	if (trust_executable_bit)
+		ce->ce_mode = create_ce_mode(st.st_mode);
+	else {
 		/* If there is an existing entry, pick the mode bits
 		 * from it, otherwise assume unexecutable.
 		 */
+		struct cache_entry *ent;
 		int pos = cache_name_pos(path, namelen);
-		if (pos >= 0)
-			ce->ce_mode = active_cache[pos]->ce_mode;
-		else if (S_ISREG(st.st_mode))
-			ce->ce_mode = create_ce_mode(S_IFREG | 0666);
+
+		ent = (0 <= pos) ? active_cache[pos] : NULL;
+		ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
 	}
 
 	if (index_path(ce->sha1, path, &st, 1))

t/t3700-add.sh

@@ -30,6 +30,16 @@ test_expect_success \
 	 *) echo fail; git-ls-files --stage xfoo1; (exit 1);;
 	 esac'
 
+test_expect_success 'git-add: filemode=0 should not get confused by symlink' '
+	rm -f xfoo1 &&
+	ln -s foo xfoo1 &&
+	git-add xfoo1 &&
+	case "`git-ls-files --stage xfoo1`" in
+	120000" "*xfoo1) echo ok;;
+	*) echo fail; git-ls-files --stage xfoo1; (exit 1);;
+	esac
+'
+
 test_expect_success \
 	'git-update-index --add: Test that executable bit is not used...' \
 	'git config core.filemode 0 &&
@@ -41,6 +51,16 @@ test_expect_success \
 	 *) echo fail; git-ls-files --stage xfoo2; (exit 1);;
 	 esac'
 
+test_expect_success 'git-add: filemode=0 should not get confused by symlink' '
+	rm -f xfoo2 &&
+	ln -s foo xfoo2 &&
+	git update-index --add xfoo2 &&
+	case "`git-ls-files --stage xfoo2`" in
+	120000" "*xfoo2) echo ok;;
+	*) echo fail; git-ls-files --stage xfoo2; (exit 1);;
+	esac
+'
+
 test_expect_success \
 	'git-update-index --add: Test that executable bit is not used...' \
 	'git config core.filemode 0 &&