[RFC][PATCH v2] git on Mac OS and precomposed unicode

["Torsten Bögershausen" <tboegi@web.de>]

Allow git on Mac OS to store file names in the index in precomposed unicode,
while the file system used decomposed unicode.

When a file called "LATIN CAPITAL LETTER A WITH DIAERESIS"
(in utf-8 encoded as 0xc3 0x84) is created,
the filesystem converts "precomposed unicode" into "decomposed unicode",
which means that readdir() will return 0x41 0xcc 0x88.
When true, git reverts the unicode decomposition of filenames.
This is useful when pulling/pushing from repositories containing utf-8
encoded filenames using precomposed utf-8 (like Linux).

This feature is automatically switched on when "git init" is run,
and the file system is doing UTF-8 decompostion.
(Which has been observed on HFS+, SMBFS and VFAT, but not on NFS)
It can be switched off by setting core.macosforcenfc=false

It is implemented by re-defining the readdir() functions.
File names are converted into precomposed UTF-8.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 Documentation/config.txt     |    9 ++
 Makefile                     |    3 +
 builtin/init-db.c            |   22 +++++
 compat/darwin.c              |  208 ++++++++++++++++++++++++++++++++++++++++++
 compat/darwin.h              |   31 ++++++
 git-compat-util.h            |    8 ++
 git.c                        |    1 +
 t/t0050-filesystem.sh        |    1 +
 t/t3910-mac-os-precompose.sh |  117 +++++++++++++++++++++++
 9 files changed, 400 insertions(+), 0 deletions(-)
 create mode 100644 compat/darwin.c
 create mode 100644 compat/darwin.h
 create mode 100755 t/t3910-mac-os-precompose.sh

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 2959390..01b9465 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -175,6 +175,15 @@ The default is false, except linkgit:git-clone[1] or linkgit:git-init[1]
 will probe and set core.ignorecase true if appropriate when the repository
 is created.
 
+core.precomposedunicode::
+	This option is only used by Mac OS implementation of git.
+	When core.precomposedunicode=true,
+	git reverts the unicode decomposition of filenames done by Mac OS.
+	This is useful when pulling/pushing from repositories containing utf-8
+	encoded filenames using precomposed unicode (like Linux).
+	When false, file names are handled fully transparent by git.
+	If in doubt, set core.precomposedunicode=false.
+
 core.trustctime::
 	If false, the ctime differences between the index and the
 	working tree are ignored; useful when the inode change time
diff --git a/Makefile b/Makefile
index b21d2f1..596900e 100644
--- a/Makefile
+++ b/Makefile
@@ -519,6 +519,7 @@ LIB_H += compat/bswap.h
 LIB_H += compat/cygwin.h
 LIB_H += compat/mingw.h
 LIB_H += compat/obstack.h
+LIB_H += compat/darwin.h
 LIB_H += compat/win32/pthread.h
 LIB_H += compat/win32/syslog.h
 LIB_H += compat/win32/poll.h
@@ -884,6 +885,8 @@ ifeq ($(uname_S),Darwin)
 	endif
 	NO_MEMMEM = YesPlease
 	USE_ST_TIMESPEC = YesPlease
+	COMPAT_OBJS += compat/darwin.o
+	BASIC_CFLAGS += -DPRECOMPOSED_UNICODE
 endif
 ifeq ($(uname_S),SunOS)
 	NEEDS_SOCKET = YesPlease
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 0dacb8b..88c9de1 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -290,6 +290,28 @@ static int create_default_files(const char *template_path)
 		strcpy(path + len, "CoNfIg");
 		if (!access(path, F_OK))
 			git_config_set("core.ignorecase", "true");
+#if defined (PRECOMPOSED_UNICODE)
+		{
+			const static char *auml_nfc = "\xc3\xa4";
+			const static char *auml_nfd = "\x61\xcc\x88";
+			int output_fd;
+			path[len] = 0;
+			strcpy(path + len, auml_nfc);
+			output_fd = open(path, O_CREAT|O_EXCL|O_RDWR, 0600);
+			if (output_fd >=0) {
+				close(output_fd);
+				path[len] = 0;
+				strcpy(path + len, auml_nfd);
+				if (0 == access(path, R_OK))
+					git_config_set("core.precomposedunicode", "true");
+				else
+					git_config_set("core.precomposedunicode", "false");
+				path[len] = 0;
+				strcpy(path + len, auml_nfc);
+				unlink(path);
+			}
+		}
+#endif
 	}
 
 	return reinit;
diff --git a/compat/darwin.c b/compat/darwin.c
new file mode 100644
index 0000000..6cf73ca
--- /dev/null
+++ b/compat/darwin.c
@@ -0,0 +1,208 @@
+#define __DARWIN_C__
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include "../cache.h"
+#include "../utf8.h"
+
+#include "darwin.h"
+
+static int mac_os_precomposed_unicode;
+const static char *repo_encoding = "UTF-8";
+const static char *path_encoding = "UTF-8-MAC";
+
+
+/* Code borrowed from utf8.c */
+#if defined(OLD_ICONV) || (defined(__sun__) && !defined(_XPG6))
+	typedef const char * iconv_ibp;
+#else
+	typedef char * iconv_ibp;
+#endif
+static char *reencode_string_iconv(const char *in, size_t insz, iconv_t conv)
+{
+	size_t outsz, outalloc;
+	char *out, *outpos;
+	iconv_ibp cp;
+
+	outsz = insz;
+	outalloc = outsz + 1; /* for terminating NUL */
+	out = xmalloc(outalloc);
+	outpos = out;
+	cp = (iconv_ibp)in;
+
+	while (1) {
+		size_t cnt = iconv(conv, &cp, &insz, &outpos, &outsz);
+
+		if (cnt == -1) {
+			size_t sofar;
+			if (errno != E2BIG) {
+				free(out);
+				iconv_close(conv);
+				return NULL;
+			}
+			/* insz has remaining number of bytes.
+			 * since we started outsz the same as insz,
+			 * it is likely that insz is not enough for
+			 * converting the rest.
+			 */
+			sofar = outpos - out;
+			outalloc = sofar + insz * 2 + 32;
+			out = xrealloc(out, outalloc);
+			outpos = out + sofar;
+			outsz = outalloc - sofar - 1;
+		}
+		else {
+			*outpos = '\0';
+			break;
+		}
+	}
+	return out;
+}
+
+static size_t
+has_utf8(const char *s, size_t maxlen, size_t *strlen_c)
+{
+	const uint8_t *utf8p = (const uint8_t*) s;
+	size_t strlen_chars = 0;
+	size_t ret = 0;
+
+	if ((!utf8p) || (!*utf8p))
+		return 0;
+
+	while((*utf8p) && maxlen) {
+		if (*utf8p & 0x80)
+			ret++;
+		strlen_chars++;
+		utf8p++;
+		maxlen--;
+	}
+	if (strlen_c)
+		*strlen_c = strlen_chars;
+
+	return ret;
+}
+
+static int
+precomposed_unicode_config(const char *var, const char *value, void *cb)
+{
+	if (!strcasecmp(var, "core.precomposedunicode")) {
+		mac_os_precomposed_unicode = git_config_bool(var, value);
+		return 0;
+	}
+	return 1;
+}
+
+void
+argv_precompose(int argc, const char **argv)
+{
+	int i = 0;
+	int first_arg = 0; /* convert everything */
+	const char *oldarg;
+	char *newarg;
+	iconv_t ic_precompose;
+
+	git_config(precomposed_unicode_config, NULL);
+	if (!mac_os_precomposed_unicode)
+		return;
+
+	ic_precompose = iconv_open(repo_encoding, path_encoding);
+	if (ic_precompose == (iconv_t) -1)
+		return;
+
+	if (!strcmp("commit", argv[0])) {
+		first_arg = argc; /* default: convert nothing */
+
+		for (i = 0; i < argc; i++) {
+			if (!strcmp(argv[i], "--")) {
+				first_arg = i + 1; /* convert args after "--" */
+				i = argc;
+				break;
+			}
+		}
+		i = first_arg;
+	}
+	while (i < argc) {
+		size_t namelen;
+		oldarg = argv[i];
+		if (has_utf8(oldarg, (size_t)-1, &namelen)) {
+			newarg = reencode_string_iconv(oldarg, namelen, ic_precompose);
+			if (newarg)
+				argv[i] = newarg;
+		}
+		i++;
+	}
+	iconv_close(ic_precompose);
+}
+
+
+DARWIN_DIR *
+darwin_opendir(const char *dirname)
+{
+	DARWIN_DIR *darwin_dir;
+	darwin_dir = malloc(sizeof(DARWIN_DIR));
+	if (!darwin_dir)
+		return NULL;
+
+	darwin_dir->dirp = opendir(dirname);
+	if (!darwin_dir->dirp) {
+		free(darwin_dir);
+		return NULL;
+	}
+	darwin_dir->ic_precompose = iconv_open(repo_encoding, path_encoding);
+	if (darwin_dir->ic_precompose == (iconv_t) -1) {
+		closedir(darwin_dir->dirp);
+		free(darwin_dir);
+		return NULL;
+	}
+
+	return darwin_dir;
+}
+
+struct dirent *
+darwin_readdir(DARWIN_DIR *darwin_dirp)
+{
+	struct dirent *res;
+	size_t namelen = 0;
+
+	res = readdir(darwin_dirp->dirp);
+	if (!res || !mac_os_precomposed_unicode || !has_utf8(res->d_name, (size_t)-1, &namelen))
+		return res;
+	else {
+		int olderrno = errno;
+		size_t outsz = sizeof(darwin_dirp->dirent_nfc.d_name) - 1; /* one for \0 */
+		char *outpos = darwin_dirp->dirent_nfc.d_name;
+		iconv_ibp cp;
+		size_t cnt;
+		size_t insz = namelen;
+		cp = (iconv_ibp)res->d_name;
+
+		/* Copy all data except the name */
+		memcpy(&darwin_dirp->dirent_nfc, res,
+		       sizeof(darwin_dirp->dirent_nfc)-sizeof(darwin_dirp->dirent_nfc.d_name));
+		errno = 0;
+
+		cnt = iconv(darwin_dirp->ic_precompose, &cp, &insz, &outpos, &outsz);
+		if (cnt < sizeof(darwin_dirp->dirent_nfc.d_name) -1) {
+			*outpos = 0;
+			errno = olderrno;
+			return &darwin_dirp->dirent_nfc;
+		}
+		errno = olderrno;
+		return res;
+	}
+}
+
+
+int
+darwin_closedir(DARWIN_DIR *darwin_dirp)
+{
+	int ret_value;
+	ret_value = closedir(darwin_dirp->dirp);
+	if (darwin_dirp->ic_precompose != (iconv_t)-1)
+		iconv_close(darwin_dirp->ic_precompose);
+	free(darwin_dirp);
+	return ret_value;
+}
diff --git a/compat/darwin.h b/compat/darwin.h
new file mode 100644
index 0000000..094f930
--- /dev/null
+++ b/compat/darwin.h
@@ -0,0 +1,31 @@
+#ifndef __DARWIN_H__
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <iconv.h>
+
+
+typedef struct {
+	iconv_t ic_precompose;
+	DIR *dirp;
+	struct dirent dirent_nfc;
+} DARWIN_DIR;
+
+char *str_precompose(const char *in, iconv_t ic_precompose);
+
+void argv_precompose(int argc, const char **argv);
+
+DARWIN_DIR *darwin_opendir(const char *dirname);
+struct dirent *darwin_readdir(DARWIN_DIR *dirp);
+int darwin_closedir(DARWIN_DIR *dirp);
+
+#ifndef __DARWIN_C__
+#define opendir(n) darwin_opendir(n)
+#define readdir(d) darwin_readdir(d)
+#define closedir(d) darwin_closedir(d)
+#define DIR DARWIN_DIR
+
+#endif  /* __DARWIN_C__ */
+
+#define  __DARWIN_H__
+#endif /* __DARWIN_H__ */
diff --git a/git-compat-util.h b/git-compat-util.h
index 230e198..859dfcf 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -90,6 +90,14 @@
 #include <windows.h>
 #endif
 
+#if defined (PRECOMPOSED_UNICODE)
+#include "compat/darwin.h"
+#else
+#define str_precompose(in,i_nfd2nfc) (NULL)
+#define argv_precompose(c,v)
+
+#endif
+
 #include <unistd.h>
 #include <stdio.h>
 #include <sys/stat.h>
diff --git a/git.c b/git.c
index 8e34903..6b2ffb7 100644
--- a/git.c
+++ b/git.c
@@ -298,6 +298,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 		    startup_info->have_repository) /* get_git_dir() may set up repo, avoid that */
 			trace_repo_setup(prefix);
 	}
+	argv_precompose(argc, argv);
 	commit_pager_choice();
 
 	if (!help && p->option & NEED_WORK_TREE)
diff --git a/t/t0050-filesystem.sh b/t/t0050-filesystem.sh
index 1542cf6..befe39e 100755
--- a/t/t0050-filesystem.sh
+++ b/t/t0050-filesystem.sh
@@ -126,6 +126,7 @@ test_expect_success "setup unicode normalization tests" '
 
   test_create_repo unicode &&
   cd unicode &&
+  git config core.precomposedunicode false &&
   touch "$aumlcdiar" &&
   git add "$aumlcdiar" &&
   git commit -m initial &&
diff --git a/t/t3910-mac-os-precompose.sh b/t/t3910-mac-os-precompose.sh
new file mode 100755
index 0000000..439e266
--- /dev/null
+++ b/t/t3910-mac-os-precompose.sh
@@ -0,0 +1,117 @@
+#!/bin/sh
+#
+# Copyright (c) 2012 Torsten Bögershausen
+#
+
+test_description='utf-8 decomposed (nfd) converted to precomposed (nfc)'
+
+. ./test-lib.sh
+
+Adiarnfc=`printf '\303\204'`
+Odiarnfc=`printf '\303\226'`
+Adiarnfd=`printf 'A\314\210'`
+Odiarnfd=`printf 'O\314\210'`
+
+mkdir junk &&
+>junk/"$Adiarnfc" &&
+case "$(cd junk && echo *)" in
+	"$Adiarnfd")
+	test_nfd=1
+	;;
+	*)	;;
+esac
+rm -rf junk
+
+if test "$test_nfd"
+then
+	test_expect_success "detect if nfd needed" '
+		precomposedunicode=`git config --bool core.precomposedunicode` &&
+		test "$precomposedunicode" = true
+	'
+	test_expect_success "setup" '
+		>x &&
+		git add x &&
+		git commit -m "1st commit" &&
+		git rm x &&
+		git commit -m "rm x"
+	'
+	test_expect_success "setup case mac" '
+		git checkout -b mac_os
+	'
+	# This will test nfd2nfc in readdir()
+	test_expect_success "add file Adiarnfc" '
+		echo f.Adiarnfc >f.$Adiarnfc &&
+		git add f.$Adiarnfc &&
+		git commit -m "add f.$Adiarnfc"
+	'
+	# This will test nfd2nfc in git stage()
+	test_expect_success "stage file d.Adiarnfd/f.Adiarnfd" '
+		mkdir d.$Adiarnfd &&
+		echo d.$Adiarnfd/f.$Adiarnfd >d.$Adiarnfd/f.$Adiarnfd &&
+		git stage d.$Adiarnfd/f.$Adiarnfd &&
+		git commit -m "add d.$Adiarnfd/f.$Adiarnfd"
+	'
+	test_expect_success "add link Adiarnfc" '
+		ln -s d.$Adiarnfd/f.$Adiarnfd l.$Adiarnfc &&
+		git add l.$Adiarnfc &&
+		git commit -m "add l.Adiarnfc"
+	'
+	# This will test git log
+	test_expect_success "git log f.Adiar" '
+		git log f.$Adiarnfc > f.Adiarnfc.log &&
+		git log f.$Adiarnfd > f.Adiarnfd.log &&
+		test -s f.Adiarnfc.log &&
+		test -s f.Adiarnfd.log &&
+		test_cmp f.Adiarnfc.log f.Adiarnfd.log &&
+		rm f.Adiarnfc.log f.Adiarnfd.log
+	'
+	# This will test git ls-files
+	test_expect_success "git lsfiles f.Adiar" '
+		git ls-files f.$Adiarnfc > f.Adiarnfc.log &&
+		git ls-files f.$Adiarnfd > f.Adiarnfd.log &&
+		test -s f.Adiarnfc.log &&
+		test -s f.Adiarnfd.log &&
+		test_cmp f.Adiarnfc.log f.Adiarnfd.log &&
+		rm f.Adiarnfc.log f.Adiarnfd.log
+	'
+	# This will test git mv
+	test_expect_success "git mv" '
+		git mv f.$Adiarnfd f.$Odiarnfc &&
+		git mv d.$Adiarnfd d.$Odiarnfc &&
+		git mv l.$Adiarnfd l.$Odiarnfc &&
+		git commit -m "mv Adiarnfd Odiarnfc"
+	'
+	# Files can be checked out as nfc
+	# And the link has been corrected from nfd to nfc
+	test_expect_success "git checkout nfc" '
+		rm f.$Odiarnfc &&
+		git checkout f.$Odiarnfc
+	'
+	# Make it possible to checkout files with their NFD names
+	test_expect_success "git checkout file nfd" '
+		rm -f f.* &&
+		git checkout f.$Odiarnfd
+	'
+	# Make it possible to checkout links with their NFD names
+	test_expect_success "git checkout link nfd" '
+		rm l.* &&
+		git checkout l.$Odiarnfd
+	'
+	test_expect_success "setup case mac2" '
+		git checkout master &&
+		git reset --hard &&
+		git checkout -b mac_os_2
+	'
+	# This will test nfd2nfc in git commit
+	test_expect_success "commit file d2.Adiarnfd/f.Adiarnfd" '
+		mkdir d2.$Adiarnfd &&
+		echo d2.$Adiarnfd/f.$Adiarnfd >d2.$Adiarnfd/f.$Adiarnfd &&
+		git add d2.$Adiarnfd/f.$Adiarnfd &&
+		git commit -m "add d2.$Adiarnfd/f.$Adiarnfd" -- d2.$Adiarnfd/f.$Adiarnfd
+	'
+else
+	 say "Skipping nfc/nfd tests"
+fi
+		#git commit -m "add d2.$Adiarnfd/f.$Adiarnfd" -- d2.$Adiarnfd/f.$Adiarnfd
+
+test_done
-- 
1.7.8.rc0.43.gb49a8