[PATCH/RFC v1 1/1] cygwin: Allow pushing to UNC paths

[tboegi@web.de]

From: Torsten Bögershausen <tboegi@web.de>

cygwin can use an UNC path like //server/share/repo
$ cd //server/share/dir
$ mkdir test
$ cd test
$ git init --bare

However, when we try to push from a local Git repository to this repo,
there are 2 problems:
- Git converts the leading "//" into a single "/".
- The remote repo is not accepted because setup.c calls
  access(getenv(DB_ENVIRONMENT), X_OK)
  and this call fails. In other words, checking the executable bit
  of a directory mounted on a SAMBA share is not reliable (and not needed).

As cygwin handles an UNC path so well, Git can support them better.
- Introduce cygwin_offset_1st_component() which keeps the leading "//",
  similar to what Git for Windows does.
- Move CYGWIN out of the POSIX in the tests for path normalization in t0060.
- Use cygwin_access() with a relaxed test for the executable bit on
  a directory pointed out by an UNC path.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 compat/cygwin.c       | 29 +++++++++++++++++++++++++++++
 compat/cygwin.h       |  7 +++++++
 config.mak.uname      |  1 +
 git-compat-util.h     |  3 +++
 t/t0060-path-utils.sh |  2 ++
 5 files changed, 42 insertions(+)
 create mode 100644 compat/cygwin.c
 create mode 100644 compat/cygwin.h

diff --git a/compat/cygwin.c b/compat/cygwin.c
new file mode 100644
index 0000000..d98e877
--- /dev/null
+++ b/compat/cygwin.c
@@ -0,0 +1,29 @@
+#include "../git-compat-util.h"
+#include "../cache.h"
+
+int cygwin_offset_1st_component(const char *path)
+{
+	const char *pos = path;
+	/* unc paths */
+	if (is_dir_sep(pos[0]) && is_dir_sep(pos[1])) {
+		/* skip server name */
+		pos = strchr(pos + 2, '/');
+		if (!pos)
+			return 0; /* Error: malformed unc path */
+
+		do {
+			pos++;
+		} while (*pos && pos[0] != '/');
+	}
+	return pos + is_dir_sep(*pos) - path;
+}
+
+#undef access
+int cygwin_access(const char *filename, int mode)
+{
+	/* the execute bit does not work on SAMBA drives */
+	if (filename[0] == '/' && filename[1] == '/' )
+		return access(filename, mode & ~X_OK);
+	else
+		return access(filename, mode);
+}
diff --git a/compat/cygwin.h b/compat/cygwin.h
new file mode 100644
index 0000000..efa12ad
--- /dev/null
+++ b/compat/cygwin.h
@@ -0,0 +1,7 @@
+int cygwin_access(const char *filename, int mode);
+#undef access
+#define access cygwin_access
+
+
+int cygwin_offset_1st_component(const char *path);
+#define offset_1st_component cygwin_offset_1st_component
diff --git a/config.mak.uname b/config.mak.uname
index adfb90b..551e465 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -184,6 +184,7 @@ ifeq ($(uname_O),Cygwin)
 	UNRELIABLE_FSTAT = UnfortunatelyYes
 	SPARSE_FLAGS = -isystem /usr/include/w32api -Wno-one-bit-signed-bitfield
 	OBJECT_CREATION_USES_RENAMES = UnfortunatelyNeedsTo
+	COMPAT_OBJS += compat/cygwin.o
 endif
 ifeq ($(uname_S),FreeBSD)
 	NEEDS_LIBICONV = YesPlease
diff --git a/git-compat-util.h b/git-compat-util.h
index 047172d..db9c22d 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -189,6 +189,9 @@
 #include <sys/sysctl.h>
 #endif
 
+#if defined(__CYGWIN__)
+#include "compat/cygwin.h"
+#endif
 #if defined(__MINGW32__)
 /* pull in Windows compatibility stuff */
 #include "compat/mingw.h"
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 444b5a4..7ea2bb5 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -70,6 +70,8 @@ ancestor() {
 case $(uname -s) in
 *MINGW*)
 	;;
+*CYGWIN*)
+	;;
 *)
 	test_set_prereq POSIX
 	;;
-- 
2.10.0