simple-ipc: work around issues with Cygwin's Unix socket emulation

Cygwin emulates Unix sockets by writing files with custom contents and
then marking them as system files.

The tricky problem is that while the file is written and its `system`
bit is set, it is still identified as a file. This caused test failures
when Git is too fast looking for the Unix sockets and then complains
that there is a plain file in the way.

Let's work around this by adding a delayed retry loop, specifically for
Cygwin.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Tested-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/simple-ipc/ipc-unix-socket.c b/compat/simple-ipc/ipc-unix-socket.c
index 4e28857a0a1e22aaa7538be2ef6d766a373dbca5..28a79289d4fd0a9d4e185cd5c9d8b19afdde70e7 100644 (file)
--- a/compat/simple-ipc/ipc-unix-socket.c
+++ b/compat/simple-ipc/ipc-unix-socket.c
@@ -35,6 +35,28 @@ enum ipc_active_state ipc_get_active_state(const char *path)
                }
        }
 
+#ifdef __CYGWIN__
+       /*
+        * Cygwin emulates Unix sockets by writing special-crafted files whose
+        * `system` bit is set.
+        *
+        * If we are too fast, Cygwin might still be in the process of marking
+        * the underlying file as a system file. Until then, we will not see a
+        * Unix socket here, but a plain file instead. Just in case that this
+        * is happening, wait a little and try again.
+        */
+       {
+               static const int delay[] = { 1, 10, 20, 40, -1 };
+               int i;
+
+               for (i = 0; S_ISREG(st.st_mode) && delay[i] > 0; i++) {
+                       sleep_millisec(delay[i]);
+                       if (lstat(path, &st) == -1)
+                               return IPC_STATE__INVALID_PATH;
+               }
+       }
+#endif
+
        /* also complain if a plain file is in the way */
        if ((st.st_mode & S_IFMT) != S_IFSOCK)
                return IPC_STATE__INVALID_PATH;