Merge branch 'tb/push-to-cygwin-unc-path' into maint

On Cygwin, similar to Windows, "git push //server/share/repository"
ought to mean a repository on a network share that can be accessed
locally, but this did not work correctly due to stripping the double
slashes at the beginning.

This may need to be heavily tested before it gets unleashed to the
wild, as the change is at a fairly low-level code and would affect
not just the code to decide if the push destination is local.  There
may be unexpected fallouts in the path normalization.

* tb/push-to-cygwin-unc-path:
  cygwin: allow pushing to UNC paths

compat/cygwin.c

@@ -0,0 +1,19 @@
+#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;
+}

compat/cygwin.h

@@ -0,0 +1,2 @@
+int cygwin_offset_1st_component(const char *path);
+#define offset_1st_component cygwin_offset_1st_component

config.mak.uname

@@ -181,6 +181,7 @@ 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

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"

t/t0060-path-utils.sh

@@ -70,6 +70,8 @@ ancestor() {
 case $(uname -s) in
 *MINGW*)
 	;;
+*CYGWIN*)
+	;;
 *)
 	test_set_prereq POSIX
 	;;