From a1be47e4ca65718ec239e4b86a44e45220237aee Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:20:42 -0400
Subject: hash-object: fix buffer reuse with --path in a subdirectory

The hash-object command uses prefix_filename() without
duplicating its return value. Since that function returns a
static buffer, the value is overwritten by subsequent calls.

This can cause incorrect results when we use --path along
with hashing a file by its relative path, both of which need
to call prefix_filename(). We overwrite the filename
computed for --path, effectively ignoring it.

We can fix this by calling xstrdup on the return value. Note
that we don't bother freeing the "vpath" instance, as it
remains valid until the program exit.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/hash-object.c b/builtin/hash-object.c
index 9028e1f..56df77b 100644
--- a/builtin/hash-object.c
+++ b/builtin/hash-object.c
@@ -115,7 +115,7 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 
 	prefix_length = prefix ? strlen(prefix) : 0;
 	if (vpath && prefix)
-		vpath = prefix_filename(prefix, prefix_length, vpath);
+		vpath = xstrdup(prefix_filename(prefix, prefix_length, vpath));
 
 	git_config(git_default_config, NULL);
 
@@ -144,11 +144,14 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 
 	for (i = 0 ; i < argc; i++) {
 		const char *arg = argv[i];
+		char *to_free = NULL;
 
 		if (0 <= prefix_length)
-			arg = prefix_filename(prefix, prefix_length, arg);
+			arg = to_free =
+				xstrdup(prefix_filename(prefix, prefix_length, arg));
 		hash_object(arg, type, no_filters ? NULL : vpath ? vpath : arg,
 			    flags, literally);
+		free(to_free);
 	}
 
 	if (stdin_paths)
diff --git a/t/t1007-hash-object.sh b/t/t1007-hash-object.sh
index c5245c5..532682f 100755
--- a/t/t1007-hash-object.sh
+++ b/t/t1007-hash-object.sh
@@ -134,6 +134,16 @@ test_expect_success 'gitattributes also work in a subdirectory' '
 	)
 '
 
+test_expect_success '--path works in a subdirectory' '
+	(
+		cd subdir &&
+		path1_sha=$(git hash-object --path=../file1 ../file0) &&
+		path0_sha=$(git hash-object --path=../file0 ../file1) &&
+		test "$file0_sha" = "$path0_sha" &&
+		test "$file1_sha" = "$path1_sha"
+	)
+'
+
 test_expect_success 'check that --no-filters option works' '
 	nofilters_file1=$(git hash-object --no-filters file1) &&
 	test "$file0_sha" = "$nofilters_file1" &&
-- 
cgit v0.10.2-6-g49f6


From 598019769cbaa38495b0c04297efa13d0f4a572e Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:21:27 -0400
Subject: prefix_filename: move docstring to header file

This is a public function, so we should make its
documentation available near the declaration.

While we're at it, we can give a few details about how it
works.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/abspath.c b/abspath.c
index b02e068..fd30aff 100644
--- a/abspath.c
+++ b/abspath.c
@@ -246,11 +246,6 @@ char *absolute_pathdup(const char *path)
 	return strbuf_detach(&sb, NULL);
 }
 
-/*
- * Unlike prefix_path, this should be used if the named file does
- * not have to interact with index entry; i.e. name of a random file
- * on the filesystem.
- */
 const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
 {
 	static struct strbuf path = STRBUF_INIT;
diff --git a/cache.h b/cache.h
index 9b2157f..a01668f 100644
--- a/cache.h
+++ b/cache.h
@@ -529,7 +529,19 @@ extern const char *setup_git_directory_gently(int *);
 extern const char *setup_git_directory(void);
 extern char *prefix_path(const char *prefix, int len, const char *path);
 extern char *prefix_path_gently(const char *prefix, int len, int *remaining, const char *path);
+
+/*
+ * Concatenate "prefix" (if len is non-zero) and "path", with no
+ * connecting characters (so "prefix" should end with a "/").
+ * Unlike prefix_path, this should be used if the named file does
+ * not have to interact with index entry; i.e. name of a random file
+ * on the filesystem.
+ *
+ * The return value may point to static storage which will be overwritten by
+ * further calls.
+ */
 extern const char *prefix_filename(const char *prefix, int len, const char *path);
+
 extern int check_filename(const char *prefix, const char *name);
 extern void verify_filename(const char *prefix,
 			    const char *name,
-- 
cgit v0.10.2-6-g49f6


From 116fb64e439d3744d0f244a51d7a6d714b7703ae Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:22:28 -0400
Subject: prefix_filename: drop length parameter

This function takes the prefix as a ptr/len pair, but in
every caller the length is exactly strlen(ptr). Let's
simplify the interface and just take the string. This saves
callers specifying it (and in some cases handling a NULL
prefix).

In a handful of cases we had the length already without
calling strlen, so this is technically slower. But it's not
likely to matter (after all, if the prefix is non-empty
we'll allocate and copy it into a buffer anyway).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/abspath.c b/abspath.c
index fd30aff..c6f4809 100644
--- a/abspath.c
+++ b/abspath.c
@@ -246,9 +246,11 @@ char *absolute_pathdup(const char *path)
 	return strbuf_detach(&sb, NULL);
 }
 
-const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
+const char *prefix_filename(const char *pfx, const char *arg)
 {
 	static struct strbuf path = STRBUF_INIT;
+	size_t pfx_len = pfx ? strlen(pfx) : 0;
+
 #ifndef GIT_WINDOWS_NATIVE
 	if (!pfx_len || is_absolute_path(arg))
 		return arg;
diff --git a/apply.c b/apply.c
index 0e2caea..b8bd5a4 100644
--- a/apply.c
+++ b/apply.c
@@ -2046,7 +2046,7 @@ static void prefix_one(struct apply_state *state, char **name)
 	char *old_name = *name;
 	if (!old_name)
 		return;
-	*name = xstrdup(prefix_filename(state->prefix, state->prefix_length, *name));
+	*name = xstrdup(prefix_filename(state->prefix, *name));
 	free(old_name);
 }
 
@@ -4815,9 +4815,7 @@ int apply_all_patches(struct apply_state *state,
 			read_stdin = 0;
 			continue;
 		} else if (0 < state->prefix_length)
-			arg = prefix_filename(state->prefix,
-					      state->prefix_length,
-					      arg);
+			arg = prefix_filename(state->prefix, arg);
 
 		fd = open(arg, O_RDONLY);
 		if (fd < 0) {
diff --git a/builtin/config.c b/builtin/config.c
index 05843a0..74f6c34 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -528,7 +528,6 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		if (!is_absolute_path(given_config_source.file) && prefix)
 			given_config_source.file =
 				xstrdup(prefix_filename(prefix,
-							strlen(prefix),
 							given_config_source.file));
 	}
 
diff --git a/builtin/hash-object.c b/builtin/hash-object.c
index 56df77b..2ea3690 100644
--- a/builtin/hash-object.c
+++ b/builtin/hash-object.c
@@ -102,7 +102,6 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 		OPT_END()
 	};
 	int i;
-	int prefix_length = -1;
 	const char *errstr = NULL;
 
 	argc = parse_options(argc, argv, NULL, hash_object_options,
@@ -113,9 +112,8 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 	else
 		prefix = setup_git_directory_gently(&nongit);
 
-	prefix_length = prefix ? strlen(prefix) : 0;
 	if (vpath && prefix)
-		vpath = xstrdup(prefix_filename(prefix, prefix_length, vpath));
+		vpath = xstrdup(prefix_filename(prefix, vpath));
 
 	git_config(git_default_config, NULL);
 
@@ -146,9 +144,8 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 		const char *arg = argv[i];
 		char *to_free = NULL;
 
-		if (0 <= prefix_length)
-			arg = to_free =
-				xstrdup(prefix_filename(prefix, prefix_length, arg));
+		if (prefix)
+			arg = to_free = xstrdup(prefix_filename(prefix, arg));
 		hash_object(arg, type, no_filters ? NULL : vpath ? vpath : arg,
 			    flags, literally);
 		free(to_free);
diff --git a/builtin/log.c b/builtin/log.c
index 281af8c..bfdc7a2 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1084,8 +1084,7 @@ static const char *set_outdir(const char *prefix, const char *output_directory)
 	if (!output_directory)
 		return prefix;
 
-	return xstrdup(prefix_filename(prefix, outdir_offset,
-				       output_directory));
+	return xstrdup(prefix_filename(prefix, output_directory));
 }
 
 static const char * const builtin_format_patch_usage[] = {
diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index e3b62f2..681f07f 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -15,7 +15,7 @@ static char *prefix_copy(const char *prefix, const char *filename)
 {
 	if (!prefix || is_absolute_path(filename))
 		return xstrdup(filename);
-	return xstrdup(prefix_filename(prefix, strlen(prefix), filename));
+	return xstrdup(prefix_filename(prefix, filename));
 }
 
 int cmd_mailinfo(int argc, const char **argv, const char *prefix)
diff --git a/builtin/merge-file.c b/builtin/merge-file.c
index 13e22a2..63cd943 100644
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -28,7 +28,6 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 	xmparam_t xmp = {{0}};
 	int ret = 0, i = 0, to_stdout = 0;
 	int quiet = 0;
-	int prefixlen = 0;
 	struct option options[] = {
 		OPT_BOOL('p', "stdout", &to_stdout, N_("send results to standard output")),
 		OPT_SET_INT(0, "diff3", &xmp.style, N_("use a diff3 based merge"), XDL_MERGE_DIFF3),
@@ -65,11 +64,8 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 			return error_errno("failed to redirect stderr to /dev/null");
 	}
 
-	if (prefix)
-		prefixlen = strlen(prefix);
-
 	for (i = 0; i < 3; i++) {
-		const char *fname = prefix_filename(prefix, prefixlen, argv[i]);
+		const char *fname = prefix_filename(prefix, argv[i]);
 		if (!names[i])
 			names[i] = argv[i];
 		if (read_mmfile(mmfs + i, fname))
@@ -90,7 +86,7 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 
 	if (ret >= 0) {
 		const char *filename = argv[0];
-		const char *fpath = prefix_filename(prefix, prefixlen, argv[0]);
+		const char *fpath = prefix_filename(prefix, argv[0]);
 		FILE *f = to_stdout ? stdout : fopen(fpath, "wb");
 
 		if (!f)
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 2549643..c803533 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -228,9 +228,7 @@ static int show_file(const char *arg, int output_prefix)
 	if ((filter & (DO_NONFLAGS|DO_NOREV)) == (DO_NONFLAGS|DO_NOREV)) {
 		if (output_prefix) {
 			const char *prefix = startup_info->prefix;
-			show(prefix_filename(prefix,
-					     prefix ? strlen(prefix) : 0,
-					     arg));
+			show(prefix_filename(prefix, arg));
 		} else
 			show(arg);
 		return 1;
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 831fe05..e38325e 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -338,7 +338,7 @@ static int add(int ac, const char **av, const char *prefix)
 	if (ac < 1 || ac > 2)
 		usage_with_options(worktree_usage, options);
 
-	path = prefix_filename(prefix, strlen(prefix), av[0]);
+	path = prefix_filename(prefix, av[0]);
 	branch = ac < 2 ? "HEAD" : av[1];
 
 	if (!strcmp(branch, "-"))
diff --git a/cache.h b/cache.h
index a01668f..0b53aef 100644
--- a/cache.h
+++ b/cache.h
@@ -540,7 +540,7 @@ extern char *prefix_path_gently(const char *prefix, int len, int *remaining, con
  * The return value may point to static storage which will be overwritten by
  * further calls.
  */
-extern const char *prefix_filename(const char *prefix, int len, const char *path);
+extern const char *prefix_filename(const char *prefix, const char *path);
 
 extern int check_filename(const char *prefix, const char *name);
 extern void verify_filename(const char *prefix,
diff --git a/diff-no-index.c b/diff-no-index.c
index df762fd..5f7317c 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -236,7 +236,7 @@ static void fixup_paths(const char **path, struct strbuf *replacement)
 void diff_no_index(struct rev_info *revs,
 		   int argc, const char **argv)
 {
-	int i, prefixlen;
+	int i;
 	const char *paths[2];
 	struct strbuf replacement = STRBUF_INIT;
 	const char *prefix = revs->prefix;
@@ -257,7 +257,6 @@ void diff_no_index(struct rev_info *revs,
 		}
 	}
 
-	prefixlen = prefix ? strlen(prefix) : 0;
 	for (i = 0; i < 2; i++) {
 		const char *p = argv[argc - 2 + i];
 		if (!strcmp(p, "-"))
@@ -266,8 +265,8 @@ void diff_no_index(struct rev_info *revs,
 			 * path that is "-", spell it as "./-".
 			 */
 			p = file_from_standard_input;
-		else if (prefixlen)
-			p = xstrdup(prefix_filename(prefix, prefixlen, p));
+		else if (prefix)
+			p = xstrdup(prefix_filename(prefix, p));
 		paths[i] = p;
 	}
 
diff --git a/diff.c b/diff.c
index a628ac3..70870b4 100644
--- a/diff.c
+++ b/diff.c
@@ -4023,7 +4023,7 @@ int diff_opt_parse(struct diff_options *options,
 	else if (!strcmp(arg, "--pickaxe-regex"))
 		options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
 	else if ((argcount = short_opt('O', av, &optarg))) {
-		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		const char *path = prefix_filename(prefix, optarg);
 		options->orderfile = xstrdup(path);
 		return argcount;
 	}
@@ -4071,7 +4071,7 @@ int diff_opt_parse(struct diff_options *options,
 	else if (!strcmp(arg, "--no-function-context"))
 		DIFF_OPT_CLR(options, FUNCCONTEXT);
 	else if ((argcount = parse_long_opt("output", av, &optarg))) {
-		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		const char *path = prefix_filename(prefix, optarg);
 		options->file = fopen(path, "w");
 		if (!options->file)
 			die_errno("Could not open '%s'", path);
diff --git a/parse-options.c b/parse-options.c
index 4fbe924..ba6cc30 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -40,7 +40,7 @@ static void fix_filename(const char *prefix, const char **file)
 	if (!file || !*file || !prefix || is_absolute_path(*file)
 	    || !strcmp("-", *file))
 		return;
-	*file = xstrdup(prefix_filename(prefix, strlen(prefix), *file));
+	*file = xstrdup(prefix_filename(prefix, *file));
 }
 
 static int opt_command_mode_error(const struct option *opt,
diff --git a/setup.c b/setup.c
index 64f922a..a76379e 100644
--- a/setup.c
+++ b/setup.c
@@ -142,7 +142,7 @@ int check_filename(const char *prefix, const char *arg)
 			return 1;
 		name = arg + 2;
 	} else if (prefix)
-		name = prefix_filename(prefix, strlen(prefix), arg);
+		name = prefix_filename(prefix, arg);
 	else
 		name = arg;
 	if (!lstat(name, &st))
diff --git a/worktree.c b/worktree.c
index fa7bc67..42dd3d5 100644
--- a/worktree.c
+++ b/worktree.c
@@ -254,7 +254,7 @@ struct worktree *find_worktree(struct worktree **list,
 	if ((wt = find_worktree_by_suffix(list, arg)))
 		return wt;
 
-	arg = prefix_filename(prefix, strlen(prefix), arg);
+	arg = prefix_filename(prefix, arg);
 	path = real_pathdup(arg, 1);
 	for (; *list; list++)
 		if (!fspathcmp(path, real_path((*list)->path)))
-- 
cgit v0.10.2-6-g49f6


From e4da43b1f063d227b5f7d2922d27458748763a2d Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:28:49 -0400
Subject: prefix_filename: return newly allocated string

The prefix_filename() function returns a pointer to static
storage, which makes it easy to use dangerously. We already
fixed one buggy caller in hash-object recently, and the
calls in apply.c are suspicious (I didn't dig in enough to
confirm that there is a bug, but we call the function once
in apply_all_patches() and then again indirectly from
parse_chunk()).

Let's make it harder to get wrong by allocating the return
value. For simplicity, we'll do this even when the prefix is
empty (and we could just return the original file pointer).
That will cause us to allocate sometimes when we wouldn't
otherwise need to, but this function isn't called in
performance critical code-paths (and it already _might_
allocate on any given call, so a caller that cares about
performance is questionable anyway).

The downside is that the callers need to remember to free()
the result to avoid leaking. Most of them already used
xstrdup() on the result, so we know they are OK. The
remainder have been converted to use free() as appropriate.

I considered retaining a prefix_filename_unsafe() for cases
where we know the static lifetime is OK (and handling the
cleanup is awkward). This is only a handful of cases,
though, and it's not worth the mental energy in worrying
about whether the "unsafe" variant is OK to use in any
situation.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/abspath.c b/abspath.c
index c6f4809..4addd1f 100644
--- a/abspath.c
+++ b/abspath.c
@@ -246,20 +246,18 @@ char *absolute_pathdup(const char *path)
 	return strbuf_detach(&sb, NULL);
 }
 
-const char *prefix_filename(const char *pfx, const char *arg)
+char *prefix_filename(const char *pfx, const char *arg)
 {
-	static struct strbuf path = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
 	size_t pfx_len = pfx ? strlen(pfx) : 0;
 
 #ifndef GIT_WINDOWS_NATIVE
 	if (!pfx_len || is_absolute_path(arg))
-		return arg;
-	strbuf_reset(&path);
+		return xstrdup(arg);
 	strbuf_add(&path, pfx, pfx_len);
 	strbuf_addstr(&path, arg);
 #else
 	/* don't add prefix to absolute paths, but still replace '\' by '/' */
-	strbuf_reset(&path);
 	if (is_absolute_path(arg))
 		pfx_len = 0;
 	else if (pfx_len)
@@ -267,5 +265,5 @@ const char *prefix_filename(const char *pfx, const char *arg)
 	strbuf_addstr(&path, arg);
 	convert_slashes(path.buf + pfx_len);
 #endif
-	return path.buf;
+	return strbuf_detach(&path, NULL);
 }
diff --git a/apply.c b/apply.c
index b8bd5a4..e6dbab2 100644
--- a/apply.c
+++ b/apply.c
@@ -2046,7 +2046,7 @@ static void prefix_one(struct apply_state *state, char **name)
 	char *old_name = *name;
 	if (!old_name)
 		return;
-	*name = xstrdup(prefix_filename(state->prefix, *name));
+	*name = prefix_filename(state->prefix, *name);
 	free(old_name);
 }
 
@@ -4805,6 +4805,7 @@ int apply_all_patches(struct apply_state *state,
 
 	for (i = 0; i < argc; i++) {
 		const char *arg = argv[i];
+		char *to_free = NULL;
 		int fd;
 
 		if (!strcmp(arg, "-")) {
@@ -4814,19 +4815,21 @@ int apply_all_patches(struct apply_state *state,
 			errs |= res;
 			read_stdin = 0;
 			continue;
-		} else if (0 < state->prefix_length)
-			arg = prefix_filename(state->prefix, arg);
+		} else
+			arg = to_free = prefix_filename(state->prefix, arg);
 
 		fd = open(arg, O_RDONLY);
 		if (fd < 0) {
 			error(_("can't open patch '%s': %s"), arg, strerror(errno));
 			res = -128;
+			free(to_free);
 			goto end;
 		}
 		read_stdin = 0;
 		set_default_whitespace_mode(state);
 		res = apply_patch(state, fd, arg, options);
 		close(fd);
+		free(to_free);
 		if (res < 0)
 			goto end;
 		errs |= res;
diff --git a/builtin/config.c b/builtin/config.c
index 74f6c34..4f49a0e 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -527,8 +527,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	else if (given_config_source.file) {
 		if (!is_absolute_path(given_config_source.file) && prefix)
 			given_config_source.file =
-				xstrdup(prefix_filename(prefix,
-							given_config_source.file));
+				prefix_filename(prefix, given_config_source.file);
 	}
 
 	if (respect_includes == -1)
diff --git a/builtin/hash-object.c b/builtin/hash-object.c
index 2ea3690..bbeaf20 100644
--- a/builtin/hash-object.c
+++ b/builtin/hash-object.c
@@ -145,7 +145,7 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 		char *to_free = NULL;
 
 		if (prefix)
-			arg = to_free = xstrdup(prefix_filename(prefix, arg));
+			arg = to_free = prefix_filename(prefix, arg);
 		hash_object(arg, type, no_filters ? NULL : vpath ? vpath : arg,
 			    flags, literally);
 		free(to_free);
diff --git a/builtin/log.c b/builtin/log.c
index bfdc7a2..670229c 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1084,7 +1084,7 @@ static const char *set_outdir(const char *prefix, const char *output_directory)
 	if (!output_directory)
 		return prefix;
 
-	return xstrdup(prefix_filename(prefix, output_directory));
+	return prefix_filename(prefix, output_directory);
 }
 
 static const char * const builtin_format_patch_usage[] = {
diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index 681f07f..cfb667a 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -11,13 +11,6 @@
 static const char mailinfo_usage[] =
 	"git mailinfo [-k | -b] [-m | --message-id] [-u | --encoding=<encoding> | -n] [--scissors | --no-scissors] <msg> <patch> < mail >info";
 
-static char *prefix_copy(const char *prefix, const char *filename)
-{
-	if (!prefix || is_absolute_path(filename))
-		return xstrdup(filename);
-	return xstrdup(prefix_filename(prefix, filename));
-}
-
 int cmd_mailinfo(int argc, const char **argv, const char *prefix)
 {
 	const char *def_charset;
@@ -60,8 +53,8 @@ int cmd_mailinfo(int argc, const char **argv, const char *prefix)
 	mi.input = stdin;
 	mi.output = stdout;
 
-	msgfile = prefix_copy(prefix, argv[1]);
-	patchfile = prefix_copy(prefix, argv[2]);
+	msgfile = prefix_filename(prefix, argv[1]);
+	patchfile = prefix_filename(prefix, argv[2]);
 
 	status = !!mailinfo(&mi, msgfile, patchfile);
 	clear_mailinfo(&mi);
diff --git a/builtin/merge-file.c b/builtin/merge-file.c
index 63cd943..47dde7c 100644
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -65,11 +65,18 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 	}
 
 	for (i = 0; i < 3; i++) {
-		const char *fname = prefix_filename(prefix, argv[i]);
+		char *fname;
+		int ret;
+
 		if (!names[i])
 			names[i] = argv[i];
-		if (read_mmfile(mmfs + i, fname))
+
+		fname = prefix_filename(prefix, argv[i]);
+		ret = read_mmfile(mmfs + i, fname);
+		free(fname);
+		if (ret)
 			return -1;
+
 		if (mmfs[i].size > MAX_XDIFF_SIZE ||
 		    buffer_is_binary(mmfs[i].ptr, mmfs[i].size))
 			return error("Cannot merge binary files: %s",
@@ -86,7 +93,7 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 
 	if (ret >= 0) {
 		const char *filename = argv[0];
-		const char *fpath = prefix_filename(prefix, argv[0]);
+		char *fpath = prefix_filename(prefix, argv[0]);
 		FILE *f = to_stdout ? stdout : fopen(fpath, "wb");
 
 		if (!f)
@@ -98,6 +105,7 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 		else if (fclose(f))
 			ret = error_errno("Could not close %s", filename);
 		free(result.ptr);
+		free(fpath);
 	}
 
 	if (ret > 127)
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index c803533..7cd01c2 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -228,7 +228,9 @@ static int show_file(const char *arg, int output_prefix)
 	if ((filter & (DO_NONFLAGS|DO_NOREV)) == (DO_NONFLAGS|DO_NOREV)) {
 		if (output_prefix) {
 			const char *prefix = startup_info->prefix;
-			show(prefix_filename(prefix, arg));
+			char *fname = prefix_filename(prefix, arg);
+			show(fname);
+			free(fname);
 		} else
 			show(arg);
 		return 1;
diff --git a/builtin/worktree.c b/builtin/worktree.c
index e38325e..9993ded 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -318,7 +318,8 @@ static int add(int ac, const char **av, const char *prefix)
 {
 	struct add_opts opts;
 	const char *new_branch_force = NULL;
-	const char *path, *branch;
+	char *path;
+	const char *branch;
 	struct option options[] = {
 		OPT__FORCE(&opts.force, N_("checkout <branch> even if already checked out in other worktree")),
 		OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
diff --git a/cache.h b/cache.h
index 0b53aef..aa6a0fb 100644
--- a/cache.h
+++ b/cache.h
@@ -537,10 +537,10 @@ extern char *prefix_path_gently(const char *prefix, int len, int *remaining, con
  * not have to interact with index entry; i.e. name of a random file
  * on the filesystem.
  *
- * The return value may point to static storage which will be overwritten by
- * further calls.
+ * The return value is always a newly allocated string (even if the
+ * prefix was empty).
  */
-extern const char *prefix_filename(const char *prefix, const char *path);
+extern char *prefix_filename(const char *prefix, const char *path);
 
 extern int check_filename(const char *prefix, const char *name);
 extern void verify_filename(const char *prefix,
diff --git a/diff-no-index.c b/diff-no-index.c
index 5f7317c..7922938 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -266,7 +266,7 @@ void diff_no_index(struct rev_info *revs,
 			 */
 			p = file_from_standard_input;
 		else if (prefix)
-			p = xstrdup(prefix_filename(prefix, p));
+			p = prefix_filename(prefix, p);
 		paths[i] = p;
 	}
 
diff --git a/diff.c b/diff.c
index 70870b4..58cb72d 100644
--- a/diff.c
+++ b/diff.c
@@ -4023,8 +4023,7 @@ int diff_opt_parse(struct diff_options *options,
 	else if (!strcmp(arg, "--pickaxe-regex"))
 		options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
 	else if ((argcount = short_opt('O', av, &optarg))) {
-		const char *path = prefix_filename(prefix, optarg);
-		options->orderfile = xstrdup(path);
+		options->orderfile = prefix_filename(prefix, optarg);
 		return argcount;
 	}
 	else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
@@ -4071,13 +4070,14 @@ int diff_opt_parse(struct diff_options *options,
 	else if (!strcmp(arg, "--no-function-context"))
 		DIFF_OPT_CLR(options, FUNCCONTEXT);
 	else if ((argcount = parse_long_opt("output", av, &optarg))) {
-		const char *path = prefix_filename(prefix, optarg);
+		char *path = prefix_filename(prefix, optarg);
 		options->file = fopen(path, "w");
 		if (!options->file)
 			die_errno("Could not open '%s'", path);
 		options->close_file = 1;
 		if (options->use_color != GIT_COLOR_ALWAYS)
 			options->use_color = GIT_COLOR_NEVER;
+		free(path);
 		return argcount;
 	} else
 		return 0;
diff --git a/parse-options.c b/parse-options.c
index ba6cc30..a23a1e6 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -40,7 +40,7 @@ static void fix_filename(const char *prefix, const char **file)
 	if (!file || !*file || !prefix || is_absolute_path(*file)
 	    || !strcmp("-", *file))
 		return;
-	*file = xstrdup(prefix_filename(prefix, *file));
+	*file = prefix_filename(prefix, *file);
 }
 
 static int opt_command_mode_error(const struct option *opt,
diff --git a/setup.c b/setup.c
index a76379e..5c7946d 100644
--- a/setup.c
+++ b/setup.c
@@ -135,6 +135,7 @@ int path_inside_repo(const char *prefix, const char *path)
 int check_filename(const char *prefix, const char *arg)
 {
 	const char *name;
+	char *to_free = NULL;
 	struct stat st;
 
 	if (starts_with(arg, ":/")) {
@@ -142,13 +143,17 @@ int check_filename(const char *prefix, const char *arg)
 			return 1;
 		name = arg + 2;
 	} else if (prefix)
-		name = prefix_filename(prefix, arg);
+		name = to_free = prefix_filename(prefix, arg);
 	else
 		name = arg;
-	if (!lstat(name, &st))
+	if (!lstat(name, &st)) {
+		free(to_free);
 		return 1; /* file exists */
-	if (errno == ENOENT || errno == ENOTDIR)
+	}
+	if (errno == ENOENT || errno == ENOTDIR) {
+		free(to_free);
 		return 0; /* file does not exist */
+	}
 	die_errno("failed to stat '%s'", arg);
 }
 
diff --git a/worktree.c b/worktree.c
index 42dd3d5..bae787c 100644
--- a/worktree.c
+++ b/worktree.c
@@ -250,16 +250,19 @@ struct worktree *find_worktree(struct worktree **list,
 {
 	struct worktree *wt;
 	char *path;
+	char *to_free = NULL;
 
 	if ((wt = find_worktree_by_suffix(list, arg)))
 		return wt;
 
-	arg = prefix_filename(prefix, arg);
+	if (prefix)
+		arg = to_free = prefix_filename(prefix, arg);
 	path = real_pathdup(arg, 1);
 	for (; *list; list++)
 		if (!fspathcmp(path, real_path((*list)->path)))
 			break;
 	free(path);
+	free(to_free);
 	return *list;
 }
 
-- 
cgit v0.10.2-6-g49f6


From af10e8b1559790d5c78fcc2a1aae5c42f3930a00 Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:30:41 -0400
Subject: prefix_filename: simplify windows #ifdef

The prefix_filename function used to do an early return when
there was no prefix on non-Windows platforms, but always
allocated on Windows so that it could call convert_slashes().

Now that the function always allocates, we can unify the
logic and make convert_slashes() the only conditional part.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/abspath.c b/abspath.c
index 4addd1f..7f1cfe9 100644
--- a/abspath.c
+++ b/abspath.c
@@ -251,18 +251,15 @@ char *prefix_filename(const char *pfx, const char *arg)
 	struct strbuf path = STRBUF_INIT;
 	size_t pfx_len = pfx ? strlen(pfx) : 0;
 
-#ifndef GIT_WINDOWS_NATIVE
-	if (!pfx_len || is_absolute_path(arg))
-		return xstrdup(arg);
-	strbuf_add(&path, pfx, pfx_len);
-	strbuf_addstr(&path, arg);
-#else
-	/* don't add prefix to absolute paths, but still replace '\' by '/' */
-	if (is_absolute_path(arg))
+	if (!pfx_len)
+		; /* nothing to prefix */
+	else if (is_absolute_path(arg))
 		pfx_len = 0;
-	else if (pfx_len)
+	else
 		strbuf_add(&path, pfx, pfx_len);
+
 	strbuf_addstr(&path, arg);
+#ifdef GIT_WINDOWS_NATIVE
 	convert_slashes(path.buf + pfx_len);
 #endif
 	return strbuf_detach(&path, NULL);
-- 
cgit v0.10.2-6-g49f6


From 3b754eedd58636926d07b14a34799a3aa7b8ebc2 Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Mon, 20 Mar 2017 21:31:27 -0400
Subject: bundle: use prefix_filename with bundle path

We may take the path to a bundle file as an argument, and
need to adjust the filename based on the prefix we
discovered while setting up the git directory. We do so
manually into a fixed-size buffer, but using
prefix_filename() is the normal way.

Besides being more concise, there are two subtle
improvements:

  1. The original inserted a "/" between the two paths, even
     though the "prefix" argument always has the "/"
     appended. That means that:

       cd subdir && git bundle verify ../foo.bundle

     was looking at (and reporting) subdir//../foo.bundle.
     Harmless, but ugly.  Using prefix_filename() gets this
     right.

  2. The original checked for an absolute path by looking
     for a leading '/'. It should have been using
     is_absolute_path(), which also covers more cases on
     Windows (backslashes and dos drive prefixes).

     But it's easier still to just pass the name to
     prefix_filename(), which handles this case
     automatically.

Note that we'll just leak the resulting buffer in the name
of simplicity, since it needs to last through the duration
of the program anyway.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/bundle.c b/builtin/bundle.c
index 4883a43..d0de59b 100644
--- a/builtin/bundle.c
+++ b/builtin/bundle.c
@@ -20,21 +20,15 @@ int cmd_bundle(int argc, const char **argv, const char *prefix)
 	struct bundle_header header;
 	const char *cmd, *bundle_file;
 	int bundle_fd = -1;
-	char buffer[PATH_MAX];
 
 	if (argc < 3)
 		usage(builtin_bundle_usage);
 
 	cmd = argv[1];
-	bundle_file = argv[2];
+	bundle_file = prefix_filename(prefix, argv[2]);
 	argc -= 2;
 	argv += 2;
 
-	if (prefix && bundle_file[0] != '/') {
-		snprintf(buffer, sizeof(buffer), "%s/%s", prefix, bundle_file);
-		bundle_file = buffer;
-	}
-
 	memset(&header, 0, sizeof(header));
 	if (strcmp(cmd, "create") && (bundle_fd =
 				read_bundle_header(bundle_file, &header)) < 0)
-- 
cgit v0.10.2-6-g49f6