fixup! gvfs: add global command pre and post hook procs

The `linux-leaks` job has become a lot more aggressive, failing the
following test cases:

- t0001.52 extensions.objectFormat is not allowed with repo version 0
- t1302.3 gitdir selection on unsupported repo
- t1302.4 gitdir not required mode
- t1302.5 gitdir required mode
- t1302.9 abort version=1 no-such-extension
- t1302.12 abort version=0 noop-v1

The reason is that the `commondir` strbuf _is_ sometimes initialized
_even if_ `discover_git_directory()` fails. The symptom:

    Direct leak of 24 byte(s) in 1 object(s) allocated from:
        #0 0x7f2e80ed8293 in __interceptor_realloc ../../../../src/libsanitizer/lsan/lsan_interceptors.cpp:98
        #1 0x5603ff6ae674 in xrealloc wrapper.c:138
        #2 0x5603ff661801 in strbuf_grow strbuf.c:101
        #3 0x5603ff662417 in strbuf_add strbuf.c:300
        #4 0x5603ff653e2b in strbuf_addstr strbuf.h:310
        #5 0x5603ff65703b in setup_git_directory_gently_1 setup.c:1329
        #6 0x5603ff65731b in discover_git_directory_reason setup.c:1388
        #7 0x5603ff55b6c0 in discover_git_directory setup.h:79
        #8 0x5603ff55b7ce in hook_path_early hook.c:35
        #9 0x5603ff55b97d in find_hook hook.c:77
        #10 0x5603ff55bcd3 in run_hooks_opt hook.c:189
        #11 0x5603ff37ca05 in run_pre_command_hook git.c:457
        #12 0x5603ff37ce0a in run_builtin git.c:532
        #13 0x5603ff37d37e in handle_builtin git.c:798
        #14 0x5603ff37d65a in run_argv git.c:867
        #15 0x5603ff37dc8e in cmd_main git.c:1007
        #16 0x5603ff48f4ee in main common-main.c:62
        #17 0x7f2e80cabd8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

The fix is easy: always release the `strbuf`s, even when the discovery
of the Git directory failed.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

hook.c

@@ -33,6 +33,8 @@ static const char *hook_path_early(const char *name, struct strbuf *result)
 		const char *early_hooks_dir = NULL;
 
 		if (discover_git_directory(&commondir, &gitdir) < 0) {
+			strbuf_release(&gitdir);
+			strbuf_release(&commondir);
 			initialized = -1;
 			return NULL;
 		}