[PATCH v2] path.c enter_repo(): fix unproper strbuf unwrapping and memory leakage

[Hui Yiqun <huiyiqun@gmail.com>]

According to strbuf.h, strbuf_detach is the sole supported method
to unwrap a memory buffer from its strbuf shell.

So we should not return the pointer of strbuf.buf directly.

What's more, some memory leakages are solved.
---
 path.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/path.c b/path.c
index 969b494..b07e5a7 100644
--- a/path.c
+++ b/path.c
@@ -625,6 +625,7 @@ const char *enter_repo(const char *path, int strict)
 {
 	static struct strbuf validated_path = STRBUF_INIT;
 	static struct strbuf used_path = STRBUF_INIT;
+	char * dbuf = NULL;
 
 	if (!path)
 		return NULL;
@@ -654,7 +655,7 @@ const char *enter_repo(const char *path, int strict)
 		if (used_path.buf[0] == '~') {
 			char *newpath = expand_user_path(used_path.buf);
 			if (!newpath)
-				return NULL;
+				goto return_null;
 			strbuf_attach(&used_path, newpath, strlen(newpath),
 				      strlen(newpath));
 		}
@@ -671,22 +672,22 @@ const char *enter_repo(const char *path, int strict)
 			strbuf_setlen(&used_path, baselen);
 		}
 		if (!suffix[i])
-			return NULL;
+			goto return_null;
 		gitfile = read_gitfile(used_path.buf);
 		if (gitfile) {
 			strbuf_reset(&used_path);
 			strbuf_addstr(&used_path, gitfile);
 		}
 		if (chdir(used_path.buf))
-			return NULL;
-		path = validated_path.buf;
+			goto return_null;
+		path = dbuf = strbuf_detach(&validated_path, NULL);
 	}
 	else {
 		const char *gitfile = read_gitfile(path);
 		if (gitfile)
 			path = gitfile;
 		if (chdir(path))
-			return NULL;
+			goto return_null;
 	}
 
 	if (is_git_directory(".")) {
@@ -695,6 +696,10 @@ const char *enter_repo(const char *path, int strict)
 		return path;
 	}
 
+return_null:
+    free(dbuf);
+	strbuf_release(&used_path);
+	strbuf_release(&validated_path);
 	return NULL;
 }
 
-- 
2.7.4