macOS: ls-files path fails if path of workdir is NFD

Under macOS, `git ls-files path` does not work (gives an error)
if the absolute 'path' contains characters in NFD (decomposed).
This happens when core.precomposeunicode is true, which is the
most common case. The bug report says:

$ cd somewhere          # some safe place, /tmp or ~/tmp etc.
$ mkdir $'u\xcc\x88'    # ü in NFD
$ cd ü                  # or cd $'u\xcc\x88' or cd $'\xc3\xbc'
$ git init
$ git ls-files $'/somewhere/u\xcc\x88'   # NFD
  fatal: /somewhere/ü: '/somewhere/ü' is outside repository at '/somewhere/ü'
$ git ls-files $'/somewhere/\xc3\xbc'    # NFC
(the same error as above)

In the 'fatal:' error message, there are three ü;
the 1st and 2nd are in NFC, the 3rd is in NFD.

Add a test case that follows the bug report, with the simplification
that the 'ü' is replaced by an 'ä', which is already used as NFD and
NFC in t0050.

Precompose the result of getcwd(), if needed, just like all other
paths we use internally.  That way, paths comparisons are all done
in NFC and we would correctly notice that the early part of the
path given as an absolute path matches the current directory.

One possible implementation would be to re-define getcwd() similar
to opendir(), readdir() and closedir(), but since there is already a
strbuf wrapper around getcwd(), and only this wrapper is used inside
the whole codebase, equip strbuf_getcwd() with a call to the newly
created function precompose_strbuf_if_needed().

Note that precompose_strbuf_if_needed() is a function under macOS,
and is a "no-op" on all other systems.

Add a missing call to precompose_string_if_needed() to this code
in setup.c :
`work_tree = precompose_string_if_needed(get_git_work_tree());`

Reported-by: Jun T <[email protected]>
Signed-off-by: Torsten Bögershausen <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

compat/precompose_utf8.c

@@ -94,6 +94,16 @@ const char *precompose_string_if_needed(const char *in)
 	return in;
 }
 
+void precompose_strbuf_if_needed(struct strbuf *sb)
+{
+	char *buf_prec = (char *)precompose_string_if_needed(sb->buf);
+	if (buf_prec != sb->buf) {
+		size_t buf_prec_len = strlen(buf_prec);
+		free(strbuf_detach(sb, NULL));
+		strbuf_attach(sb, buf_prec, buf_prec_len, buf_prec_len + 1);
+	}
+}
+
 const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix)
 {
 	int i = 0;

compat/precompose_utf8.h

@@ -30,6 +30,7 @@ typedef struct {
 
 const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix);
 const char *precompose_string_if_needed(const char *in);
+void precompose_strbuf_if_needed(struct strbuf *sb);
 void probe_utf8_pathname_composition(void);
 
 PREC_DIR *precompose_utf8_opendir(const char *dirname);

git-compat-util.h

@@ -331,6 +331,7 @@ static inline const char *precompose_string_if_needed(const char *in)
 	return in;
 }
 
+#define precompose_strbuf_if_needed(a)
 #define probe_utf8_pathname_composition()
 #endif
 

setup.c

@@ -48,7 +48,7 @@ static int abspath_part_inside_repo(char *path)
 	size_t wtlen;
 	char *path0;
 	int off;
-	const char *work_tree = get_git_work_tree();
+	const char *work_tree = precompose_string_if_needed(get_git_work_tree());
 	struct strbuf realpath = STRBUF_INIT;
 
 	if (!work_tree)

strbuf.c

@@ -569,6 +569,7 @@ int strbuf_getcwd(struct strbuf *sb)
 		strbuf_grow(sb, guessed_len);
 		if (getcwd(sb->buf, sb->alloc)) {
 			strbuf_setlen(sb, strlen(sb->buf));
+			precompose_strbuf_if_needed(sb);
 			return 0;
 		}
 

t/t0050-filesystem.sh

@@ -156,4 +156,30 @@ test_expect_success CASE_INSENSITIVE_FS 'checkout with no pathspec and a case in
 	)
 '
 
+test_expect_success 'git ls-files under NFD' '
+	(
+		mkdir -p "somewhere/$aumlcdiar" &&
+		mypwd=$PWD &&
+		cd "somewhere/$aumlcdiar" &&
+		git init &&
+		git --literal-pathspecs ls-files "$mypwd/somewhere/$aumlcdiar" 2>err &&
+		>expected &&
+		test_cmp expected err
+	)
+'
+
+# Re-do the same test. Note: global core.precomposeunicode is changed
+test_expect_success 'git ls-files under NFD. global precompose false' '
+	test_when_finished "git config --global --unset core.precomposeunicode" &&
+	(
+		mypwd=$PWD &&
+		cd "somewhere/$aumlcdiar" &&
+		git config --global core.precomposeunicode false &&
+		git config core.precomposeunicode true &&
+		git --literal-pathspecs ls-files "$mypwd/somewhere/$aumlcdiar" 2>err &&
+		>expected &&
+		test_cmp expected err
+	)
+'
+
 test_done