Make core.sharedRepository work under cygwin 1.7

When core.sharedRepository is used, set_shared_perm() in path.c
needs lstat() to return the correct POSIX permissions.

The default for cygwin is core.ignoreCygwinFSTricks = false, which
means that the fast implementation in do_stat() is used instead of
lstat().

lstat() under cygwin uses the Windows security model to implement
POSIX-like permissions.  The user, group or everyone bits can be set
individually.

do_stat() simplifes the file permission bits, and may return a wrong
value.  The read-only attribute of a file is used to calculate the
permissions, resulting in either rw-r--r-- or r--r--r--

One effect of the simplified do_stat() is that t1301 fails.

Add a function cygwin_get_st_mode_bits() which returns the POSIX
permissions.  When not compiling for cygwin, true_mode_bits() in
path.c is used.

Side note:

t1301 passes under cygwin 1.5.

The "user write" bit is synchronized with the "read only" attribute
of a file:

    $ chmod 444 x
    $ attrib x
    A    R     C:\temp\pt\x

    cygwin 1.7 would show
    A          C:\temp\pt\x

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/compat/cygwin.c b/compat/cygwin.c
index 542885887..871b41d23 100644
--- a/compat/cygwin.c
+++ b/compat/cygwin.c
@@ -1,3 +1,4 @@
+#define CYGWIN_C
 #define WIN32_LEAN_AND_MEAN
 #ifdef CYGWIN_V15_WIN32API
 #include "../git-compat-util.h"
@@ -10,6 +11,18 @@
 #endif
 #include "../cache.h" /* to read configuration */
 
+/*
+ * Return POSIX permission bits, regardless of core.ignorecygwinfstricks
+ */
+int cygwin_get_st_mode_bits(const char *path, int *mode)
+{
+	struct stat st;
+	if (lstat(path, &st) < 0)
+		return -1;
+	*mode = st.st_mode;
+	return 0;
+}
+
 static inline void filetime_to_timespec(const FILETIME *ft, struct timespec *ts)
 {
 	long long winTime = ((long long)ft->dwHighDateTime << 32) +