mingw: support long paths

Windows paths are typically limited to MAX_PATH = 260 characters, even
though the underlying NTFS file system supports paths up to 32,767 chars.
This limitation is also evident in Windows Explorer, cmd.exe and many
other applications (including IDEs).

Particularly annoying is that most Windows APIs return bogus error codes
if a relative path only barely exceeds MAX_PATH in conjunction with the
current directory, e.g. ERROR_PATH_NOT_FOUND / ENOENT instead of the
infinitely more helpful ERROR_FILENAME_EXCED_RANGE / ENAMETOOLONG.

Many Windows wide char APIs support longer than MAX_PATH paths through the
file namespace prefix ('\\?\' or '\\?\UNC\') followed by an absolute path.
Notable exceptions include functions dealing with executables and the
current directory (CreateProcess, LoadLibrary, Get/SetCurrentDirectory) as
well as the entire shell API (ShellExecute, SHGetSpecialFolderPath...).

Introduce a handle_long_path function to check the length of a specified
path properly (and fail with ENAMETOOLONG), and to optionally expand long
paths using the '\\?\' file namespace prefix. Short paths will not be
modified, so we don't need to worry about device names (NUL, CON, AUX).

Contrary to MSDN docs, the GetFullPathNameW function doesn't seem to be
limited to MAX_PATH (at least not on Win7), so we can use it to do the
heavy lifting of the conversion (translate '/' to '\', eliminate '.' and
'..', and make an absolute path).

Add long path error checking to xutftowcs_path for APIs with hard MAX_PATH
limit.

Add a new MAX_LONG_PATH constant and xutftowcs_long_path function for APIs
that support long paths.

While improved error checking is always active, long paths support must be
explicitly enabled via 'core.longpaths' option. This is to prevent end
users to shoot themselves in the foot by checking out files that Windows
Explorer, cmd/bash or their favorite IDE cannot handle.

Test suite:
Test the case is when the full pathname length of a dir is close
to 260 (MAX_PATH).
Bug report and an original reproducer by Andrey Rogozhnikov:
msysgit#122 (comment)

[jes: adjusted test number to avoid conflicts, added support for
chdir(), etc]

Thanks-to: Martin W. Kirst <maki@bitkings.de>
Thanks-to: Doug Kelly <dougk.ff7@gmail.com>
Original-test-by: Andrey Rogozhnikov <rogozhnikov.andrey@gmail.com>
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Documentation/config/core.txt

@@ -676,6 +676,13 @@ core.fscache::
 Git for Windows uses this to bulk-read and cache lstat data of entire
 directories (instead of doing lstat file by file).
 
+core.longpaths::
+	Enable long path (> 260) support for builtin commands in Git for
+	Windows. This is disabled by default, as long paths are not supported
+	by Windows Explorer, cmd.exe and the Git for Windows tool chain
+	(msys, bash, tcl, perl...). Only enable this if you know what you're
+	doing and are prepared to live with a few quirks.
+
 core.unsetenvvars::
 	Windows-only: comma-separated list of environment variables'
 	names that need to be unset before spawning any other process.

compat/mingw.c

@@ -247,6 +247,27 @@ static enum hide_dotfiles_type hide_dotfiles = HIDE_DOTFILES_DOTGITONLY;
 static char *unset_environment_variables;
 int core_fscache;
 
+int are_long_paths_enabled(void)
+{
+	/* default to `false` during initialization */
+	static const int fallback = 0;
+
+	static int enabled = -1;
+
+	if (enabled < 0) {
+		/* avoid infinite recursion */
+		if (!the_repository)
+			return fallback;
+
+		if (the_repository->config &&
+		    the_repository->config->hash_initialized &&
+		    git_config_get_bool("core.longpaths", &enabled) < 0)
+			enabled = 0;
+	}
+
+	return enabled < 0 ? fallback : enabled;
+}
+
 int mingw_core_config(const char *var, const char *value,
 		      const struct config_context *ctx, void *cb)
 {
@@ -309,8 +330,8 @@ static wchar_t *normalize_ntpath(wchar_t *wbuf)
 int mingw_unlink(const char *pathname)
 {
 	int ret, tries = 0;
-	wchar_t wpathname[MAX_PATH];
-	if (xutftowcs_path(wpathname, pathname) < 0)
+	wchar_t wpathname[MAX_LONG_PATH];
+	if (xutftowcs_long_path(wpathname, pathname) < 0)
 		return -1;
 
 	if (DeleteFileW(wpathname))
@@ -342,7 +363,7 @@ static int is_dir_empty(const wchar_t *wpath)
 {
 	WIN32_FIND_DATAW findbuf;
 	HANDLE handle;
-	wchar_t wbuf[MAX_PATH + 2];
+	wchar_t wbuf[MAX_LONG_PATH + 2];
 	wcscpy(wbuf, wpath);
 	wcscat(wbuf, L"\\*");
 	handle = FindFirstFileW(wbuf, &findbuf);
@@ -363,7 +384,7 @@ static int is_dir_empty(const wchar_t *wpath)
 int mingw_rmdir(const char *pathname)
 {
 	int ret, tries = 0;
-	wchar_t wpathname[MAX_PATH];
+	wchar_t wpathname[MAX_LONG_PATH];
 	struct stat st;
 
 	/*
@@ -385,7 +406,7 @@ int mingw_rmdir(const char *pathname)
 		return -1;
 	}
 
-	if (xutftowcs_path(wpathname, pathname) < 0)
+	if (xutftowcs_long_path(wpathname, pathname) < 0)
 		return -1;
 
 	while ((ret = _wrmdir(wpathname)) == -1 && tries < ARRAY_SIZE(delay)) {
@@ -464,15 +485,18 @@ static int set_hidden_flag(const wchar_t *path, int set)
 int mingw_mkdir(const char *path, int mode)
 {
 	int ret;
-	wchar_t wpath[MAX_PATH];
+	wchar_t wpath[MAX_LONG_PATH];
 
 	if (!is_valid_win32_path(path, 0)) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	if (xutftowcs_path(wpath, path) < 0)
+	/* CreateDirectoryW path limit is 248 (MAX_PATH - 8.3 file name) */
+	if (xutftowcs_path_ex(wpath, path, MAX_LONG_PATH, -1, 248,
+			      are_long_paths_enabled()) < 0)
 		return -1;
+
 	ret = _wmkdir(wpath);
 	if (!ret && needs_hiding(path))
 		return set_hidden_flag(wpath, 1);
@@ -559,7 +583,7 @@ int mingw_open (const char *filename, int oflags, ...)
 	va_list args;
 	unsigned mode;
 	int fd, create = (oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL);
-	wchar_t wfilename[MAX_PATH];
+	wchar_t wfilename[MAX_LONG_PATH];
 	open_fn_t open_fn;
 
 	va_start(args, oflags);
@@ -587,7 +611,7 @@ int mingw_open (const char *filename, int oflags, ...)
 
 	if (filename && !strcmp(filename, "/dev/null"))
 		wcscpy(wfilename, L"nul");
-	else if (xutftowcs_path(wfilename, filename) < 0)
+	else if (xutftowcs_long_path(wfilename, filename) < 0)
 		return -1;
 
 	fd = open_fn(wfilename, oflags, mode);
@@ -645,14 +669,14 @@ FILE *mingw_fopen (const char *filename, const char *otype)
 {
 	int hide = needs_hiding(filename);
 	FILE *file;
-	wchar_t wfilename[MAX_PATH], wotype[4];
+	wchar_t wfilename[MAX_LONG_PATH], wotype[4];
 	if (filename && !strcmp(filename, "/dev/null"))
 		wcscpy(wfilename, L"nul");
 	else if (!is_valid_win32_path(filename, 1)) {
 		int create = otype && strchr(otype, 'w');
 		errno = create ? EINVAL : ENOENT;
 		return NULL;
-	} else if (xutftowcs_path(wfilename, filename) < 0)
+	} else if (xutftowcs_long_path(wfilename, filename) < 0)
 		return NULL;
 
 	if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@@ -674,14 +698,14 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
 {
 	int hide = needs_hiding(filename);
 	FILE *file;
-	wchar_t wfilename[MAX_PATH], wotype[4];
+	wchar_t wfilename[MAX_LONG_PATH], wotype[4];
 	if (filename && !strcmp(filename, "/dev/null"))
 		wcscpy(wfilename, L"nul");
 	else if (!is_valid_win32_path(filename, 1)) {
 		int create = otype && strchr(otype, 'w');
 		errno = create ? EINVAL : ENOENT;
 		return NULL;
-	} else if (xutftowcs_path(wfilename, filename) < 0)
+	} else if (xutftowcs_long_path(wfilename, filename) < 0)
 		return NULL;
 
 	if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
@@ -730,7 +754,7 @@ ssize_t mingw_write(int fd, const void *buf, size_t len)
 		if (GetFileType(h) == FILE_TYPE_PIPE)
 			errno = EPIPE;
 		else {
-			wchar_t path[MAX_PATH];
+			wchar_t path[MAX_LONG_PATH];
 			DWORD ret = GetFinalPathNameByHandleW(h, path,
 							ARRAY_SIZE(path), 0);
 			UINT drive_type = ret > 0 && ret < ARRAY_SIZE(path) ?
@@ -756,27 +780,33 @@ ssize_t mingw_write(int fd, const void *buf, size_t len)
 
 int mingw_access(const char *filename, int mode)
 {
-	wchar_t wfilename[MAX_PATH];
+	wchar_t wfilename[MAX_LONG_PATH];
 	if (!strcmp("nul", filename) || !strcmp("/dev/null", filename))
 		return 0;
-	if (xutftowcs_path(wfilename, filename) < 0)
+	if (xutftowcs_long_path(wfilename, filename) < 0)
 		return -1;
 	/* X_OK is not supported by the MSVCRT version */
 	return _waccess(wfilename, mode & ~X_OK);
 }
 
+/* cached length of current directory for handle_long_path */
+static int current_directory_len = 0;
+
 int mingw_chdir(const char *dirname)
 {
-	wchar_t wdirname[MAX_PATH];
-	if (xutftowcs_path(wdirname, dirname) < 0)
+	int result;
+	wchar_t wdirname[MAX_LONG_PATH];
+	if (xutftowcs_long_path(wdirname, dirname) < 0)
 		return -1;
-	return _wchdir(wdirname);
+	result = _wchdir(wdirname);
+	current_directory_len = GetCurrentDirectoryW(0, NULL);
+	return result;
 }
 
 int mingw_chmod(const char *filename, int mode)
 {
-	wchar_t wfilename[MAX_PATH];
-	if (xutftowcs_path(wfilename, filename) < 0)
+	wchar_t wfilename[MAX_LONG_PATH];
+	if (xutftowcs_long_path(wfilename, filename) < 0)
 		return -1;
 	return _wchmod(wfilename, mode);
 }
@@ -824,8 +854,8 @@ static int has_valid_directory_prefix(wchar_t *wfilename)
 static int do_lstat(int follow, const char *file_name, struct stat *buf)
 {
 	WIN32_FILE_ATTRIBUTE_DATA fdata;
-	wchar_t wfilename[MAX_PATH];
-	if (xutftowcs_path(wfilename, file_name) < 0)
+	wchar_t wfilename[MAX_LONG_PATH];
+	if (xutftowcs_long_path(wfilename, file_name) < 0)
 		return -1;
 
 	if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) {
@@ -996,10 +1026,10 @@ int mingw_utime (const char *file_name, const struct utimbuf *times)
 	FILETIME mft, aft;
 	int rc;
 	DWORD attrs;
-	wchar_t wfilename[MAX_PATH];
+	wchar_t wfilename[MAX_LONG_PATH];
 	HANDLE osfilehandle;
 
-	if (xutftowcs_path(wfilename, file_name) < 0)
+	if (xutftowcs_long_path(wfilename, file_name) < 0)
 		return -1;
 
 	/* must have write permission */
@@ -1082,6 +1112,7 @@ char *mingw_mktemp(char *template)
 	wchar_t wtemplate[MAX_PATH];
 	int offset = 0;
 
+	/* we need to return the path, thus no long paths here! */
 	if (xutftowcs_path(wtemplate, template) < 0)
 		return NULL;
 
@@ -1733,6 +1764,10 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 
 	if (*argv && !strcmp(cmd, *argv))
 		wcmd[0] = L'\0';
+	/*
+	 * Paths to executables and to the current directory do not support
+	 * long paths, therefore we cannot use xutftowcs_long_path() here.
+	 */
 	else if (xutftowcs_path(wcmd, cmd) < 0)
 		return -1;
 	if (dir && xutftowcs_path(wdir, dir) < 0)
@@ -2381,8 +2416,9 @@ int mingw_rename(const char *pold, const char *pnew)
 {
 	DWORD attrs, gle;
 	int tries = 0;
-	wchar_t wpold[MAX_PATH], wpnew[MAX_PATH];
-	if (xutftowcs_path(wpold, pold) < 0 || xutftowcs_path(wpnew, pnew) < 0)
+	wchar_t wpold[MAX_LONG_PATH], wpnew[MAX_LONG_PATH];
+	if (xutftowcs_long_path(wpold, pold) < 0 ||
+	    xutftowcs_long_path(wpnew, pnew) < 0)
 		return -1;
 
 	/*
@@ -2696,9 +2732,9 @@ int mingw_raise(int sig)
 
 int link(const char *oldpath, const char *newpath)
 {
-	wchar_t woldpath[MAX_PATH], wnewpath[MAX_PATH];
-	if (xutftowcs_path(woldpath, oldpath) < 0 ||
-		xutftowcs_path(wnewpath, newpath) < 0)
+	wchar_t woldpath[MAX_LONG_PATH], wnewpath[MAX_LONG_PATH];
+	if (xutftowcs_long_path(woldpath, oldpath) < 0 ||
+	    xutftowcs_long_path(wnewpath, newpath) < 0)
 		return -1;
 
 	if (!CreateHardLinkW(wnewpath, woldpath, NULL)) {
@@ -2766,8 +2802,8 @@ int mingw_is_mount_point(struct strbuf *path)
 {
 	WIN32_FIND_DATAW findbuf = { 0 };
 	HANDLE handle;
-	wchar_t wfilename[MAX_PATH];
-	int wlen = xutftowcs_path(wfilename, path->buf);
+	wchar_t wfilename[MAX_LONG_PATH];
+	int wlen = xutftowcs_long_path(wfilename, path->buf);
 	if (wlen < 0)
 		die(_("could not get long path for '%s'"), path->buf);
 
@@ -2912,9 +2948,9 @@ static size_t append_system_bin_dirs(char *path, size_t size)
 
 static int is_system32_path(const char *path)
 {
-	WCHAR system32[MAX_PATH], wpath[MAX_PATH];
+	WCHAR system32[MAX_LONG_PATH], wpath[MAX_LONG_PATH];
 
-	if (xutftowcs_path(wpath, path) < 0 ||
+	if (xutftowcs_long_path(wpath, path) < 0 ||
 	    !GetSystemDirectoryW(system32, ARRAY_SIZE(system32)) ||
 	    _wcsicmp(system32, wpath))
 		return 0;
@@ -3282,6 +3318,68 @@ int is_valid_win32_path(const char *path, int allow_literal_nul)
 	}
 }
 
+int handle_long_path(wchar_t *path, int len, int max_path, int expand)
+{
+	int result;
+	wchar_t buf[MAX_LONG_PATH];
+
+	/*
+	 * we don't need special handling if path is relative to the current
+	 * directory, and current directory + path don't exceed the desired
+	 * max_path limit. This should cover > 99 % of cases with minimal
+	 * performance impact (git almost always uses relative paths).
+	 */
+	if ((len < 2 || (!is_dir_sep(path[0]) && path[1] != ':')) &&
+	    (current_directory_len + len < max_path))
+		return len;
+
+	/*
+	 * handle everything else:
+	 * - absolute paths: "C:\dir\file"
+	 * - absolute UNC paths: "\\server\share\dir\file"
+	 * - absolute paths on current drive: "\dir\file"
+	 * - relative paths on other drive: "X:file"
+	 * - prefixed paths: "\\?\...", "\\.\..."
+	 */
+
+	/* convert to absolute path using GetFullPathNameW */
+	result = GetFullPathNameW(path, MAX_LONG_PATH, buf, NULL);
+	if (!result) {
+		errno = err_win_to_posix(GetLastError());
+		return -1;
+	}
+
+	/*
+	 * return absolute path if it fits within max_path (even if
+	 * "cwd + path" doesn't due to '..' components)
+	 */
+	if (result < max_path) {
+		wcscpy(path, buf);
+		return result;
+	}
+
+	/* error out if we shouldn't expand the path or buf is too small */
+	if (!expand || result >= MAX_LONG_PATH - 6) {
+		errno = ENAMETOOLONG;
+		return -1;
+	}
+
+	/* prefix full path with "\\?\" or "\\?\UNC\" */
+	if (buf[0] == '\\') {
+		/* ...unless already prefixed */
+		if (buf[1] == '\\' && (buf[2] == '?' || buf[2] == '.'))
+			return len;
+
+		wcscpy(path, L"\\\\?\\UNC\\");
+		wcscpy(path + 8, buf + 2);
+		return result + 6;
+	} else {
+		wcscpy(path, L"\\\\?\\");
+		wcscpy(path + 4, buf);
+		return result + 4;
+	}
+}
+
 #if !defined(_MSC_VER)
 /*
  * Disable MSVCRT command line wildcard expansion (__getmainargs called from
@@ -3443,6 +3541,9 @@ int wmain(int argc, const wchar_t **wargv)
 	/* initialize Unicode console */
 	winansi_init();
 
+	/* init length of current directory for handle_long_path */
+	current_directory_len = GetCurrentDirectoryW(0, NULL);
+
 	/* invoke the real main() using our utf8 version of argv. */
 	exit_status = main(argc, argv);
 

compat/mingw.h

@@ -12,6 +12,7 @@ typedef _sigset_t sigset_t;
 #endif
 
 extern int core_fscache;
+int are_long_paths_enabled(void);
 
 struct config_context;
 int mingw_core_config(const char *var, const char *value,
@@ -520,6 +521,42 @@ int is_path_owned_by_current_sid(const char *path, struct strbuf *report);
 int is_valid_win32_path(const char *path, int allow_literal_nul);
 #define is_valid_path(path) is_valid_win32_path(path, 0)
 
+/**
+ * Max length of long paths (exceeding MAX_PATH). The actual maximum supported
+ * by NTFS is 32,767 (* sizeof(wchar_t)), but we choose an arbitrary smaller
+ * value to limit required stack memory.
+ */
+#define MAX_LONG_PATH 4096
+
+/**
+ * Handles paths that would exceed the MAX_PATH limit of Windows Unicode APIs.
+ *
+ * With expand == false, the function checks for over-long paths and fails
+ * with ENAMETOOLONG. The path parameter is not modified, except if cwd + path
+ * exceeds max_path, but the resulting absolute path doesn't (e.g. due to
+ * eliminating '..' components). The path parameter must point to a buffer
+ * of max_path wide characters.
+ *
+ * With expand == true, an over-long path is automatically converted in place
+ * to an absolute path prefixed with '\\?\', and the new length is returned.
+ * The path parameter must point to a buffer of MAX_LONG_PATH wide characters.
+ *
+ * Parameters:
+ * path: path to check and / or convert
+ * len: size of path on input (number of wide chars without \0)
+ * max_path: max short path length to check (usually MAX_PATH = 260, but just
+ * 248 for CreateDirectoryW)
+ * expand: false to only check the length, true to expand the path to a
+ * '\\?\'-prefixed absolute path
+ *
+ * Return:
+ * length of the resulting path, or -1 on failure
+ *
+ * Errors:
+ * ENAMETOOLONG if path is too long
+ */
+int handle_long_path(wchar_t *path, int len, int max_path, int expand);
+
 /**
  * Converts UTF-8 encoded string to UTF-16LE.
  *
@@ -578,18 +615,46 @@ static inline int xutftowcs(wchar_t *wcs, const char *utf, size_t wcslen)
 }
 
 /**
- * Simplified file system specific variant of xutftowcsn, assumes output
- * buffer size is MAX_PATH wide chars and input string is \0-terminated,
- * fails with ENAMETOOLONG if input string is too long.
+ * Simplified file system specific wrapper of xutftowcsn and handle_long_path.
+ * Converts ERANGE to ENAMETOOLONG. If expand is true, wcs must be at least
+ * MAX_LONG_PATH wide chars (see handle_long_path).
  */
-static inline int xutftowcs_path(wchar_t *wcs, const char *utf)
+static inline int xutftowcs_path_ex(wchar_t *wcs, const char *utf,
+		size_t wcslen, int utflen, int max_path, int expand)
 {
-	int result = xutftowcsn(wcs, utf, MAX_PATH, -1);
+	int result = xutftowcsn(wcs, utf, wcslen, utflen);
 	if (result < 0 && errno == ERANGE)
 		errno = ENAMETOOLONG;
+	if (result >= 0)
+		result = handle_long_path(wcs, result, max_path, expand);
 	return result;
 }
 
+/**
+ * Simplified file system specific variant of xutftowcsn, assumes output
+ * buffer size is MAX_PATH wide chars and input string is \0-terminated,
+ * fails with ENAMETOOLONG if input string is too long. Typically used for
+ * Windows APIs that don't support long paths, e.g. SetCurrentDirectory,
+ * LoadLibrary, CreateProcess...
+ */
+static inline int xutftowcs_path(wchar_t *wcs, const char *utf)
+{
+	return xutftowcs_path_ex(wcs, utf, MAX_PATH, -1, MAX_PATH, 0);
+}
+
+/**
+ * Simplified file system specific variant of xutftowcsn for Windows APIs
+ * that support long paths via '\\?\'-prefix, assumes output buffer size is
+ * MAX_LONG_PATH wide chars, fails with ENAMETOOLONG if input string is too
+ * long. The 'core.longpaths' git-config option controls whether the path
+ * is only checked or expanded to a long path.
+ */
+static inline int xutftowcs_long_path(wchar_t *wcs, const char *utf)
+{
+	return xutftowcs_path_ex(wcs, utf, MAX_LONG_PATH, -1, MAX_PATH,
+				 are_long_paths_enabled());
+}
+
 /**
  * Converts UTF-16LE encoded string to UTF-8.
  *

compat/win32/dirent.c

@@ -65,19 +65,24 @@ static int dirent_closedir(dirent_DIR *dir)
 
 DIR *dirent_opendir(const char *name)
 {
-	wchar_t pattern[MAX_PATH + 2]; /* + 2 for '/' '*' */
+	wchar_t pattern[MAX_LONG_PATH + 2]; /* + 2 for "\*" */
 	WIN32_FIND_DATAW fdata;
 	HANDLE h;
 	int len;
 	dirent_DIR *dir;
 
-	/* convert name to UTF-16 and check length < MAX_PATH */
-	if ((len = xutftowcs_path(pattern, name)) < 0)
+	/* convert name to UTF-16 and check length */
+	if ((len = xutftowcs_path_ex(pattern, name, MAX_LONG_PATH, -1,
+				     MAX_PATH - 2,
+				     are_long_paths_enabled())) < 0)
 		return NULL;
 
-	/* append optional '/' and wildcard '*' */
+	/*
+	 * append optional '\' and wildcard '*'. Note: we need to use '\' as
+	 * Windows doesn't translate '/' to '\' for "\\?\"-prefixed paths.
+	 */
 	if (len && !is_dir_sep(pattern[len - 1]))
-		pattern[len++] = '/';
+		pattern[len++] = '\\';
 	pattern[len++] = '*';
 	pattern[len] = 0;
 
@@ -90,7 +95,7 @@ DIR *dirent_opendir(const char *name)
 	}
 
 	/* initialize DIR structure and copy first dir entry */
-	dir = xmalloc(sizeof(dirent_DIR) + MAX_PATH);
+	dir = xmalloc(sizeof(dirent_DIR) + MAX_LONG_PATH);
 	dir->base_dir.preaddir = (struct dirent *(*)(DIR *dir)) dirent_readdir;
 	dir->base_dir.pclosedir = (int (*)(DIR *dir)) dirent_closedir;
 	dir->dd_handle = h;

compat/win32/fscache.c

@@ -80,7 +80,7 @@ struct fsentry {
 struct heap_fsentry {
 	union {
 		struct fsentry ent;
-		char dummy[sizeof(struct fsentry) + MAX_PATH];
+		char dummy[sizeof(struct fsentry) + MAX_LONG_PATH];
 	} u;
 };
 
@@ -123,7 +123,7 @@ static void fsentry_init(struct fsentry *fse, struct fsentry *list,
 			 const char *name, size_t len)
 {
 	fse->list = list;
-	if (len > MAX_PATH)
+	if (len > MAX_LONG_PATH)
 		BUG("Trying to allocate fsentry for long path '%.*s'",
 		    (int)len, name);
 	memcpy(fse->dirent.d_name, name, len);
@@ -224,7 +224,7 @@ static struct fsentry *fseentry_create_entry(struct fscache *cache,
 static struct fsentry *fsentry_create_list(struct fscache *cache, const struct fsentry *dir,
 					   int *dir_not_found)
 {
-	wchar_t pattern[MAX_PATH];
+	wchar_t pattern[MAX_LONG_PATH];
 	NTSTATUS status;
 	IO_STATUS_BLOCK iosb;
 	PFILE_FULL_DIR_INFORMATION di;
@@ -235,13 +235,11 @@ static struct fsentry *fsentry_create_list(struct fscache *cache, const struct f
 
 	*dir_not_found = 0;
 
-	/* convert name to UTF-16 and check length < MAX_PATH */
-	if ((wlen = xutftowcsn(pattern, dir->dirent.d_name, MAX_PATH,
-			       dir->len)) < 0) {
-		if (errno == ERANGE)
-			errno = ENAMETOOLONG;
+	/* convert name to UTF-16 and check length */
+	if ((wlen = xutftowcs_path_ex(pattern, dir->dirent.d_name,
+				      MAX_LONG_PATH, dir->len, MAX_PATH - 2,
+				      are_long_paths_enabled())) < 0)
 		return NULL;
-	}
 
 	/* handle CWD */
 	if (!wlen) {

t/t2031-checkout-long-paths.sh

@@ -0,0 +1,102 @@
+#!/bin/sh
+
+test_description='checkout long paths on Windows
+
+Ensures that Git for Windows can deal with long paths (>260) enabled via core.longpaths'
+
+. ./test-lib.sh
+
+if test_have_prereq !MINGW
+then
+	skip_all='skipping MINGW specific long paths test'
+	test_done
+fi
+
+test_expect_success setup '
+	p=longpathxx && # -> 10
+	p=$p$p$p$p$p && # -> 50
+	p=$p$p$p$p$p && # -> 250
+
+	path=${p}/longtestfile && # -> 263 (MAX_PATH = 260)
+
+	blob=$(echo foobar | git hash-object -w --stdin) &&
+
+	printf "100644 %s 0\t%s\n" "$blob" "$path" |
+	git update-index --add --index-info &&
+	git commit -m initial -q
+'
+
+test_expect_success 'checkout of long paths without core.longpaths fails' '
+	git config core.longpaths false &&
+	test_must_fail git checkout -f 2>error &&
+	grep -q "Filename too long" error &&
+	test ! -d longpa*
+'
+
+test_expect_success 'checkout of long paths with core.longpaths works' '
+	git config core.longpaths true &&
+	git checkout -f &&
+	test_path_is_file longpa*/longtestfile
+'
+
+test_expect_success 'update of long paths' '
+	echo frotz >>$(ls longpa*/longtestfile) &&
+	echo $path > expect &&
+	git ls-files -m > actual &&
+	test_cmp expect actual &&
+	git add $path &&
+	git commit -m second &&
+	git grep "frotz" HEAD -- $path
+'
+
+test_expect_success cleanup '
+	# bash cannot delete the trash dir if it contains a long path
+	# lets help cleaning up (unless in debug mode)
+	if test -z "$debug"
+	then
+		rm -rf longpa~1
+	fi
+'
+
+# check that the template used in the test won't be too long:
+abspath="$(pwd)"/testdir
+test ${#abspath} -gt 230 ||
+test_set_prereq SHORTABSPATH
+
+test_expect_success SHORTABSPATH 'clean up path close to MAX_PATH' '
+	p=/123456789abcdef/123456789abcdef/123456789abcdef/123456789abc/ef &&
+	p=y$p$p$p$p &&
+	subdir="x$(echo "$p" | tail -c $((253 - ${#abspath})) - )" &&
+	# Now, $abspath/$subdir has exactly 254 characters, and is inside CWD
+	p2="$abspath/$subdir" &&
+	test 254 = ${#p2} &&
+
+	# Be careful to overcome path limitations of the MSys tools and split
+	# the $subdir into two parts. ($subdir2 has to contain 16 chars and a
+	# slash somewhere following; that is why we asked for abspath <= 230 and
+	# why we placed a slash near the end of the $subdir template.)
+	subdir2=${subdir#????????????????*/} &&
+	subdir1=testdir/${subdir%/$subdir2} &&
+	mkdir -p "$subdir1" &&
+	i=0 &&
+	# The most important case is when absolute path is 258 characters long,
+	# and that will be when i == 4.
+	while test $i -le 7
+	do
+		mkdir -p $subdir2 &&
+		touch $subdir2/one-file &&
+		mv ${subdir2%%/*} "$subdir1/" &&
+		subdir2=z${subdir2} &&
+		i=$(($i+1)) ||
+		exit 1
+	done &&
+
+	# now check that git is able to clear the tree:
+	(cd testdir &&
+	 git init &&
+	 git config core.longpaths yes &&
+	 git clean -fdx) &&
+	test ! -d "$subdir1"
+'
+
+test_done

t/t7429-submodule-long-path.sh

@@ -11,15 +11,20 @@ This test verifies that "git submodule" initialization, update and clones work,
 TEST_NO_CREATE_REPO=1
 . ./test-lib.sh
 
-longpath=""
-for (( i=0; i<4; i++ )); do
-	longpath="0123456789abcdefghijklmnopqrstuvwxyz$longpath"
-done
-# Pick a substring maximum of 90 characters
-# This should be good, since we'll add on a lot for temp directories
-longpath=${longpath:0:90}; export longpath
+# cloning a submodule calls is_git_directory("$path/../.git/modules/$path"),
+# which effectively limits the maximum length to PATH_MAX / 2 minus some
+# overhead; start with 3 * 36 = 108 chars (test 2 fails if >= 110)
+longpath36=0123456789abcdefghijklmnopqrstuvwxyz
+longpath180=$longpath36$longpath36$longpath36$longpath36$longpath36
 
-test_expect_failure 'submodule with a long path' '
+# the git database must fit within PATH_MAX, which limits the submodule name
+# to PATH_MAX - len(pwd) - ~90 (= len("/objects//") + 40-byte sha1 + some
+# overhead from the test case)
+pwd=$(pwd)
+pwdlen=$(echo "$pwd" | wc -c)
+longpath=$(echo $longpath180 | cut -c 1-$((170-$pwdlen)))
+
+test_expect_success 'submodule with a long path' '
 	git config --global protocol.file.allow always &&
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git -c init.defaultBranch=long init --bare remote &&
@@ -59,7 +64,7 @@ test_expect_failure 'submodule with a long path' '
 	)
 '
 
-test_expect_failure 'recursive submodule with a long path' '
+test_expect_success 'recursive submodule with a long path' '
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
 	git -c init.defaultBranch=long init --bare super &&
 	test_create_repo child &&
@@ -101,6 +106,5 @@ test_expect_failure 'recursive submodule with a long path' '
 		)
 	)
 '
-unset longpath
 
 test_done