[PATCH v4 1/1] MacOS: precompose_argv_prefix()

[tboegi@web.de]

From: Torsten Bögershausen <tboegi@web.de>

The following sequence leads to a "BUG" assertion running under MacOS:

  DIR=git-test-restore-p
  Adiarnfd=$(printf 'A\314\210')
  DIRNAME=xx${Adiarnfd}yy
  mkdir $DIR &&
  cd $DIR &&
  git init &&
  mkdir $DIRNAME &&
  cd $DIRNAME &&
  echo "Initial" >file &&
  git add file &&
  echo "One more line" >>file &&
  echo y | git restore -p .

 Initialized empty Git repository in /tmp/git-test-restore-p/.git/
 BUG: pathspec.c:495: error initializing pathspec_item
 Cannot close git diff-index --cached --numstat
 [snip]

The command `git restore` is run from a directory inside a Git repo.
Git needs to split the $CWD into 2 parts:
The path to the repo and "the rest", if any.
"The rest" becomes a "prefix" later used inside the pathspec code.

As an example, "/path/to/repo/dir-inside-repå" would determine
"/path/to/repo" as the root of the repo, the place where the
configuration file .git/config is found.

The rest becomes the prefix ("dir-inside-repå"), from where the
pathspec machinery expands the ".", more about this later.
If there is a decomposed form, (making the decomposing visible like this),
"dir-inside-rep°a" doesn't match "dir-inside-repå".

Git commands need to:

 (a) read the configuration variable "core.precomposeunicode"
 (b) precocompose argv[]
 (c) precompose the prefix, if there was any

The first commit,
76759c7dff53 "git on Mac OS and precomposed unicode"
addressed (a) and (b).

The call to precompose_argv() was added into parse-options.c,
because that seemed to be a good place when the patch was written.

Commands that don't use parse-options need to do (a) and (b) themselfs.

The commands `diff-files`, `diff-index`, `diff-tree` and `diff`
learned (a) and (b) in
commit 90a78b83e0b8 "diff: run arguments through precompose_argv"

Branch names (or refs in general) using decomposed code points
resulting in decomposed file names had been fixed in
commit 8e712ef6fc97 "Honor core.precomposeUnicode in more places"

The bug report from above shows 2 things:
- more commands need to handle precomposed unicode
- (c) should be implemented for all commands using pathspecs

Solution:
precompose_argv() now handles the prefix (if needed), and is renamed into
precompose_argv_prefix().

Inside this function the config variable core.precomposeunicode is read
into the global variable precomposed_unicode, as before.
This reading is skipped if precomposed_unicode had been read before.

The original patch for preocomposed unicode, 76759c7dff53, placed
precompose_argv() into parse-options.c
Now add it into git.c (as well) for commands that don't use parse-options.
Note that precompose() may be called twice - it is idempotent.

There is certainly room for cleanups - this change intends to be a bug fix.
Cleanups needs more tests in e.g. t/t3910-mac-os-precompose.sh, and should
be done in future commits.

[1] git-bugreport-2021-01-06-1209.txt (git can't deal with special characters)
[2] https://lore.kernel.org/git/A102844A-9501-4A86-854D-E3B387D378AA@icloud.com/

Reported-by: Daniel Troger <random_n0body@icloud.com>
Helped-By: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 Changes since V3:
 - Make clear that precomposing twice doesn't do anything bad (idempotent)
 - Add "" around $DIRNAME in t/t3910-mac-os-precompose.sh, as suggested by Junio
   (I don't have a strong preference here, but "cut and paste" is a good point)
 - And yes, there may be more work to be done. For the moment I would like to
   get this merged into git.git, and address the rest later.

 builtin/diff-files.c         |  2 +-
 builtin/diff-index.c         |  2 +-
 builtin/diff-tree.c          |  2 +-
 builtin/diff.c               |  2 +-
 builtin/submodule--helper.c  |  2 +-
 compat/precompose_utf8.c     | 52 +++++++++++++++++++++++-------------
 compat/precompose_utf8.h     |  2 +-
 git-compat-util.h            |  4 +--
 git.c                        |  2 +-
 parse-options.c              |  2 +-
 t/t3910-mac-os-precompose.sh | 16 +++++++++++
 11 files changed, 59 insertions(+), 29 deletions(-)

diff --git a/builtin/diff-files.c b/builtin/diff-files.c
index 1e352dd8f7..e3851dd1c0 100644
--- a/builtin/diff-files.c
+++ b/builtin/diff-files.c
@@ -35,7 +35,7 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
 	 */
 	rev.diffopt.ita_invisible_in_index = 1;

-	precompose_argv(argc, argv);
+	prefix = precompose_argv_prefix(argc, argv, prefix);

 	argc = setup_revisions(argc, argv, &rev, NULL);
 	while (1 < argc && argv[1][0] == '-') {
diff --git a/builtin/diff-index.c b/builtin/diff-index.c
index 7f5281c461..c33d7af478 100644
--- a/builtin/diff-index.c
+++ b/builtin/diff-index.c
@@ -25,7 +25,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
 	repo_init_revisions(the_repository, &rev, prefix);
 	rev.abbrev = 0;
-	precompose_argv(argc, argv);
+	prefix = precompose_argv_prefix(argc, argv, prefix);

 	argc = setup_revisions(argc, argv, &rev, NULL);
 	for (i = 1; i < argc; i++) {
diff --git a/builtin/diff-tree.c b/builtin/diff-tree.c
index 9fc95e959f..178d12f07f 100644
--- a/builtin/diff-tree.c
+++ b/builtin/diff-tree.c
@@ -126,7 +126,7 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 	memset(&s_r_opt, 0, sizeof(s_r_opt));
 	s_r_opt.tweak = diff_tree_tweak_rev;

-	precompose_argv(argc, argv);
+	prefix = precompose_argv_prefix(argc, argv, prefix);
 	argc = setup_revisions(argc, argv, opt, &s_r_opt);

 	memset(&w, 0, sizeof(w));
diff --git a/builtin/diff.c b/builtin/diff.c
index 780c33877f..3c87c95967 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -452,7 +452,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)

 	init_diff_ui_defaults();
 	git_config(git_diff_ui_config, NULL);
-	precompose_argv(argc, argv);
+	prefix = precompose_argv_prefix(argc, argv, prefix);

 	repo_init_revisions(the_repository, &rev, prefix);

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index c2bd882d17..9d505a6329 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -1257,7 +1257,7 @@ static int compute_summary_module_list(struct object_id *head_oid,
 	git_config(git_diff_basic_config, NULL);
 	init_revisions(&rev, info->prefix);
 	rev.abbrev = 0;
-	precompose_argv(diff_args.nr, diff_args.v);
+	precompose_argv_prefix(diff_args.nr, diff_args.v, NULL);
 	setup_revisions(diff_args.nr, diff_args.v, &rev, NULL);
 	rev.diffopt.output_format = DIFF_FORMAT_NO_OUTPUT | DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = submodule_summary_callback;
diff --git a/compat/precompose_utf8.c b/compat/precompose_utf8.c
index 136250fbf6..ec560565a8 100644
--- a/compat/precompose_utf8.c
+++ b/compat/precompose_utf8.c
@@ -60,32 +60,46 @@ void probe_utf8_pathname_composition(void)
 	strbuf_release(&path);
 }

-
-void precompose_argv(int argc, const char **argv)
+static inline const char *precompose_string_if_needed(const char *in)
 {
-	int i = 0;
-	const char *oldarg;
-	char *newarg;
-	iconv_t ic_precompose;
+	size_t inlen;
+	size_t outlen;
+	if (has_non_ascii(in, (size_t)-1, &inlen)) {
+		iconv_t ic_prec;
+		char *out;
+		if (precomposed_unicode < 0)
+			git_config_get_bool("core.precomposeunicode", &precomposed_unicode);
+		if (precomposed_unicode != 1)
+			return in;
+		ic_prec = iconv_open(repo_encoding, path_encoding);
+		if (ic_prec == (iconv_t) -1)
+			return in;
+
+		out = reencode_string_iconv(in, inlen, ic_prec, 0, &outlen);
+		if (out) {
+			if (outlen == inlen && !memcmp(in, out, outlen))
+				free(out); /* no need to return indentical */
+			else
+				in = out;
+		}
+		iconv_close(ic_prec);

-	if (precomposed_unicode != 1)
-		return;
+	}
+	return in;
+}

-	ic_precompose = iconv_open(repo_encoding, path_encoding);
-	if (ic_precompose == (iconv_t) -1)
-		return;
+const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix)
+{
+	int i = 0;

 	while (i < argc) {
-		size_t namelen;
-		oldarg = argv[i];
-		if (has_non_ascii(oldarg, (size_t)-1, &namelen)) {
-			newarg = reencode_string_iconv(oldarg, namelen, ic_precompose, 0, NULL);
-			if (newarg)
-				argv[i] = newarg;
-		}
+		argv[i] = precompose_string_if_needed(argv[i]);
 		i++;
 	}
-	iconv_close(ic_precompose);
+	if (prefix) {
+		prefix = precompose_string_if_needed(prefix);
+	}
+	return prefix;
 }


diff --git a/compat/precompose_utf8.h b/compat/precompose_utf8.h
index 6f843d3e1a..d70b84665c 100644
--- a/compat/precompose_utf8.h
+++ b/compat/precompose_utf8.h
@@ -28,7 +28,7 @@ typedef struct {
 	struct dirent_prec_psx *dirent_nfc;
 } PREC_DIR;

-void precompose_argv(int argc, const char **argv);
+const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix);
 void probe_utf8_pathname_composition(void);

 PREC_DIR *precompose_utf8_opendir(const char *dirname);
diff --git a/git-compat-util.h b/git-compat-util.h
index 104993b975..93d9b4b7af 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -252,9 +252,9 @@ typedef unsigned long uintptr_t;
 #ifdef PRECOMPOSE_UNICODE
 #include "compat/precompose_utf8.h"
 #else
-static inline void precompose_argv(int argc, const char **argv)
+static inline const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix)
 {
-	; /* nothing */
+	return prefix;
 }
 #define probe_utf8_pathname_composition()
 #endif
diff --git a/git.c b/git.c
index a00a0a4d94..16a485fbe7 100644
--- a/git.c
+++ b/git.c
@@ -420,7 +420,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 			int nongit_ok;
 			prefix = setup_git_directory_gently(&nongit_ok);
 		}
-
+		prefix = precompose_argv_prefix(argc, argv, prefix);
 		if (use_pager == -1 && p->option & (RUN_SETUP | RUN_SETUP_GENTLY) &&
 		    !(p->option & DELAY_PAGER_CONFIG))
 			use_pager = check_pager_config(p->cmd);
diff --git a/parse-options.c b/parse-options.c
index f0507432ee..fbea16eaf5 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -869,7 +869,7 @@ int parse_options(int argc, const char **argv, const char *prefix,
 		usage_with_options(usagestr, options);
 	}

-	precompose_argv(argc, argv);
+	precompose_argv_prefix(argc, argv, NULL);
 	free(real_options);
 	free(ctx.alias_groups);
 	return parse_options_end(&ctx);
diff --git a/t/t3910-mac-os-precompose.sh b/t/t3910-mac-os-precompose.sh
index 54ce19e353..bc632a03ed 100755
--- a/t/t3910-mac-os-precompose.sh
+++ b/t/t3910-mac-os-precompose.sh
@@ -191,6 +191,22 @@ test_expect_failure 'handle existing decomposed filenames' '
 	test_must_be_empty untracked
 '

+test_expect_success "unicode decomposed: git restore -p . " '
+	DIRNAMEPWD=dir.Odiarnfc &&
+	DIRNAMEINREPO=dir.$Adiarnfc &&
+	export DIRNAMEPWD DIRNAMEINREPO &&
+	git init "$DIRNAMEPWD" &&
+	(
+		cd "$DIRNAMEPWD" &&
+		mkdir "$DIRNAMEINREPO" &&
+		cd "$DIRNAMEINREPO" &&
+		echo "Initial" >file &&
+		git add file &&
+		echo "More stuff" >>file &&
+		echo y | git restore -p .
+	)
+'
+
 # Test if the global core.precomposeunicode stops autosensing
 # Must be the last test case
 test_expect_success "respect git config --global core.precomposeunicode" '
--
2.30.0.155.g66e871b664