fsmonitor: handle differences between Windows named pipe functions

CreateNamedPipeW is perfectly happy accepting pipe names with seemingly
embedded escape charcters (e.g. \b), WaitNamedPipeW is not and incorrectly
returns ERROR_FILE_NOT_FOUND when clearly a named pipe, succesfully created
with CreateNamedPipeW, exists.

For example, this network path is problemmatic:
\\batfs-sb29-cifs\vmgr\sbs29\my_git_repo

In order to work around this issue, rather than using the path to the
worktree directly as the name of the pipe, instead use the hash of the
worktree path.

Signed-off-by: Eric DeCosta <[email protected]>

Author: edecosta-mw

compat/simple-ipc/ipc-win32.c

@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "hex.h"
 #include "simple-ipc.h"
 #include "strbuf.h"
 #include "pkt-line.h"
@@ -17,27 +18,27 @@
 static int initialize_pipe_name(const char *path, wchar_t *wpath, size_t alloc)
 {
 	int off = 0;
-	struct strbuf realpath = STRBUF_INIT;
-
-	if (!strbuf_realpath(&realpath, path, 0))
-		return -1;
+	int ret = 0;
+	git_SHA_CTX sha1ctx;
+	struct strbuf real_path = STRBUF_INIT;
+	struct strbuf pipe_name = STRBUF_INIT;
+	unsigned char hash[GIT_MAX_RAWSZ];
 
-	off = swprintf(wpath, alloc, L"\\\\.\\pipe\\");
-	if (xutftowcs(wpath + off, realpath.buf, alloc - off) < 0)
+	if (!strbuf_realpath(&real_path, path, 0))
 		return -1;
 
-	/* Handle drive prefix */
-	if (wpath[off] && wpath[off + 1] == L':') {
-		wpath[off + 1] = L'_';
-		off += 2;
-	}
+	git_SHA1_Init(&sha1ctx);
+	git_SHA1_Update(&sha1ctx, real_path.buf, real_path.len);
+	git_SHA1_Final(hash, &sha1ctx);
+	strbuf_release(&real_path);
 
-	for (; wpath[off]; off++)
-		if (wpath[off] == L'/')
-			wpath[off] = L'\\';
+	strbuf_addf(&pipe_name, "git-fsmonitor-%s", hash_to_hex(hash));
+	off = swprintf(wpath, alloc, L"\\\\.\\pipe\\");
+	if (xutftowcs(wpath + off, pipe_name.buf, alloc - off) < 0)
+		ret = -1;
 
-	strbuf_release(&realpath);
-	return 0;
+	strbuf_release(&pipe_name);
+	return ret;
 }
 
 static enum ipc_active_state get_active_state(wchar_t *pipe_path)