win32: enable `p_utimes` for readonly files

Instead of failing to set the timestamp of a read-only file (like any
object file), set it writable temporarily to update the timestamp.

3 files changed, 160 insertions, 88 deletions

diff --git a/src/posix.h b/src/posix.h
index bd5a98e26..d26371bca 100644
--- a/src/posix.h
+++ b/src/posix.h
@@ -24,6 +24,10 @@
 #define _S_IFLNK S_IFLNK
 #endif
 
+#ifndef S_IWUSR
+#define S_IWUSR 00200
+#endif
+
 #ifndef S_IXUSR
 #define S_IXUSR 00100
 #endif
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index bf132966d..c7094dbb9 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -363,44 +363,6 @@ int p_lstat_posixly(const char *filename, struct stat *buf)
 	return do_lstat(filename, buf, true);
 }
 
-int p_utimes(const char *filename, const struct p_timeval times[2])
-{
-	int fd, error;
-
-	if ((fd = p_open(filename, O_RDWR)) < 0)
-		return fd;
-
-	error = p_futimes(fd, times);
-
-	close(fd);
-	return error;
-}
-
-int p_futimes(int fd, const struct p_timeval times[2])
-{
-	HANDLE handle;
-	FILETIME atime = {0}, mtime = {0};
-
-	if (times == NULL) {
-		SYSTEMTIME st;
-
-		GetSystemTime(&st);
-		SystemTimeToFileTime(&st, &atime);
-		SystemTimeToFileTime(&st, &mtime);
-	} else {
-		git_win32__timeval_to_filetime(&atime, times[0]);
-		git_win32__timeval_to_filetime(&mtime, times[1]);
-	}
-
-	if ((handle = (HANDLE)_get_osfhandle(fd)) == INVALID_HANDLE_VALUE)
-		return -1;
-
-	if (SetFileTime(handle, NULL, &atime, &mtime) == 0)
-		return -1;
-
-	return 0;
-}
-
 int p_readlink(const char *path, char *buf, size_t bufsiz)
 {
 	git_win32_path path_w, target_w;
@@ -433,23 +395,69 @@ int p_symlink(const char *old, const char *new)
 	return git_futils_fake_symlink(old, new);
 }
 
+struct open_opts {
+	DWORD access;
+	DWORD sharing;
+	SECURITY_ATTRIBUTES security;
+	DWORD creation_disposition;
+	DWORD attributes;
+	int osf_flags;
+};
+
+GIT_INLINE(void) open_opts_from_posix(struct open_opts *opts, int flags, mode_t mode)
+{
+	memset(opts, 0, sizeof(struct open_opts));
+
+	switch (flags & (O_WRONLY | O_RDWR)) {
+	case O_WRONLY:
+		opts->access = GENERIC_WRITE;
+		break;
+	case O_RDWR:
+		opts->access = GENERIC_READ | GENERIC_WRITE;
+		break;
+	default:
+		opts->access = GENERIC_READ;
+		break;
+	}
+
+	opts->sharing = (DWORD)git_win32__createfile_sharemode;
+
+	switch (flags & (O_CREAT | O_TRUNC | O_EXCL)) {
+	case O_CREAT | O_EXCL:
+	case O_CREAT | O_TRUNC | O_EXCL:
+		opts->creation_disposition = CREATE_NEW;
+		break;
+	case O_CREAT | O_TRUNC:
+		opts->creation_disposition = CREATE_ALWAYS;
+		break;
+	case O_TRUNC:
+		opts->creation_disposition = TRUNCATE_EXISTING;
+		break;
+	case O_CREAT:
+		opts->creation_disposition = OPEN_ALWAYS;
+		break;
+	default:
+		opts->creation_disposition = OPEN_EXISTING;
+		break;
+	}
+
+	opts->attributes = ((flags & O_CREAT) && !(mode & S_IWRITE)) ?
+		FILE_ATTRIBUTE_READONLY : FILE_ATTRIBUTE_NORMAL;
+	opts->osf_flags = flags & (O_RDONLY | O_APPEND);
+
+	opts->security.nLength = sizeof(SECURITY_ATTRIBUTES);
+	opts->security.lpSecurityDescriptor = NULL;
+	opts->security.bInheritHandle = 0;
+}
+
 GIT_INLINE(int) open_once(
 	const wchar_t *path,
-	DWORD access,
-	DWORD sharing,
-	DWORD creation_disposition,
-	DWORD attributes,
-	int osf_flags)
+	struct open_opts *opts)
 {
-	SECURITY_ATTRIBUTES security;
 	int fd;
 
-	security.nLength = sizeof(SECURITY_ATTRIBUTES);
-	security.lpSecurityDescriptor = NULL;
-	security.bInheritHandle = 0;
-
-	HANDLE handle = CreateFileW(path, access, sharing, &security,
-		creation_disposition, attributes, 0);
+	HANDLE handle = CreateFileW(path, opts->access, opts->sharing,
+		&opts->security, opts->creation_disposition, opts->attributes, 0);
 
 	if (handle == INVALID_HANDLE_VALUE) {
 		if (last_error_retryable())
@@ -459,14 +467,17 @@ GIT_INLINE(int) open_once(
 		return -1;
 	}
 
-	return _open_osfhandle((intptr_t)handle, osf_flags);
+	if ((fd = _open_osfhandle((intptr_t)handle, opts->osf_flags)) < 0)
+		CloseHandle(handle);
+
+	return fd;
 }
 
 int p_open(const char *path, int flags, ...)
 {
 	git_win32_path wpath;
 	mode_t mode = 0;
-	DWORD access, sharing, creation, attributes, osf_flags;
+	struct open_opts opts = {0};
 
 	if (git_win32_path_from_utf8(wpath, path) < 0)
 		return -1;
@@ -479,51 +490,83 @@ int p_open(const char *path, int flags, ...)
 		va_end(arg_list);
 	}
 
-	switch (flags & (O_WRONLY | O_RDWR)) {
-	case O_WRONLY:
-		access = GENERIC_WRITE;
-		break;
-	case O_RDWR:
-		access = GENERIC_READ | GENERIC_WRITE;
-		break;
-	default:
-		access = GENERIC_READ;
-		break;
+	open_opts_from_posix(&opts, flags, mode);
+
+	do_with_retries(
+		open_once(wpath, &opts),
+		0);
+}
+
+int p_creat(const char *path, mode_t mode)
+{
+	return p_open(path, O_WRONLY | O_CREAT | O_TRUNC, mode);
+}
+
+int p_utimes(const char *path, const struct p_timeval times[2])
+{
+	git_win32_path wpath;
+	int fd, error;
+	DWORD attrs_orig, attrs_new = 0;
+	struct open_opts opts = { 0 };
+
+	if (git_win32_path_from_utf8(wpath, path) < 0)
+		return -1;
+
+	attrs_orig = GetFileAttributesW(wpath);
+
+	if (attrs_orig & FILE_ATTRIBUTE_READONLY) {
+		attrs_new = attrs_orig & ~FILE_ATTRIBUTE_READONLY;
+
+		if (!SetFileAttributesW(wpath, attrs_new)) {
+			giterr_set(GITERR_OS, "failed to set attributes");
+			return -1;
+		}
 	}
 
-	sharing = (DWORD)git_win32__createfile_sharemode;
+	open_opts_from_posix(&opts, O_RDWR, 0);
 
-	switch (flags & (O_CREAT | O_TRUNC | O_EXCL)) {
-	case O_CREAT | O_EXCL:
-	case O_CREAT | O_TRUNC | O_EXCL:
-		creation = CREATE_NEW;
-		break;
-	case O_CREAT | O_TRUNC:
-		creation = CREATE_ALWAYS;
-		break;
-	case O_TRUNC:
-		creation = TRUNCATE_EXISTING;
-		break;
-	case O_CREAT:
-		creation = OPEN_ALWAYS;
-		break;
-	default:
-		creation = OPEN_EXISTING;
-		break;
+	if ((fd = open_once(wpath, &opts)) < 0) {
+		error = -1;
+		goto done;
 	}
 
-	attributes = ((flags & O_CREAT) && !(mode & S_IWRITE)) ?
-		FILE_ATTRIBUTE_READONLY : FILE_ATTRIBUTE_NORMAL;
-	osf_flags = flags & (O_RDONLY | O_APPEND);
+	error = p_futimes(fd, times);
+	close(fd);
 
-	do_with_retries(
-		open_once(wpath, access, sharing, creation, attributes, osf_flags),
-		0);
+done:
+	if (attrs_orig != attrs_new) {
+		DWORD os_error = GetLastError();
+		SetFileAttributesW(wpath, attrs_orig);
+		SetLastError(os_error);
+	}
+
+	return error;
 }
 
-int p_creat(const char *path, mode_t mode)
+int p_futimes(int fd, const struct p_timeval times[2])
 {
-	return p_open(path, O_WRONLY | O_CREAT | O_TRUNC, mode);
+	HANDLE handle;
+	FILETIME atime = { 0 }, mtime = { 0 };
+
+	if (times == NULL) {
+		SYSTEMTIME st;
+
+		GetSystemTime(&st);
+		SystemTimeToFileTime(&st, &atime);
+		SystemTimeToFileTime(&st, &mtime);
+	}
+	else {
+		git_win32__timeval_to_filetime(&atime, times[0]);
+		git_win32__timeval_to_filetime(&mtime, times[1]);
+	}
+
+	if ((handle = (HANDLE)_get_osfhandle(fd)) == INVALID_HANDLE_VALUE)
+		return -1;
+
+	if (SetFileTime(handle, NULL, &atime, &mtime) == 0)
+		return -1;
+
+	return 0;
 }
 
 int p_getcwd(char *buffer_out, size_t size)
diff --git a/tests/odb/freshen.c b/tests/odb/freshen.c
index f41e4361e..9d3cf51dc 100644
--- a/tests/odb/freshen.c
+++ b/tests/odb/freshen.c
@@ -55,6 +55,31 @@ void test_odb_freshen__loose_blob(void)
 	cl_assert(before.st_mtime < after.st_mtime);
 }
 
+#define UNIQUE_STR     "doesnt exist in the odb yet\n"
+#define UNIQUE_BLOB_ID "78a87d0b8878c5953b9a63015ff4e22a3d898826"
+#define UNIQUE_BLOB_FN "78/a87d0b8878c5953b9a63015ff4e22a3d898826"
+
+void test_odb_freshen__readonly_object(void)
+{
+	git_oid expected_id, id;
+	struct stat before, after;
+
+	cl_git_pass(git_oid_fromstr(&expected_id, UNIQUE_BLOB_ID));
+
+	cl_git_pass(git_blob_create_frombuffer(&id, repo, UNIQUE_STR, CONST_STRLEN(UNIQUE_STR)));
+	cl_assert_equal_oid(&expected_id, &id);
+
+	set_time_wayback(&before, UNIQUE_BLOB_FN);
+	cl_assert((before.st_mode & S_IWUSR) == 0);
+
+	cl_git_pass(git_blob_create_frombuffer(&id, repo, UNIQUE_STR, CONST_STRLEN(UNIQUE_STR)));
+	cl_assert_equal_oid(&expected_id, &id);
+	cl_must_pass(p_lstat("testrepo.git/objects/" UNIQUE_BLOB_FN, &after));
+
+	cl_assert(before.st_atime < after.st_atime);
+	cl_assert(before.st_mtime < after.st_mtime);
+}
+
 #define LOOSE_TREE_ID "944c0f6e4dfa41595e6eb3ceecdb14f50fe18162"
 #define LOOSE_TREE_FN "94/4c0f6e4dfa41595e6eb3ceecdb14f50fe18162"