[PATCH 15/22] resolve_symlink(): use a strbuf internally

[Michael Haggerty <mhagger@alum.mit.edu>]

This removes another place where the path name is arbitrarily limited.

This gets rid of a warning

    %s: symlink too long

even though strbuf_readlink() in fact still limits the length of what
it can handle to something like 2*PATH_MAX.  But (1) the limit is now
much longer, and (2) strbuf_readlink() doesn't return enough
information to distinguish this problem from other symlink-reading
problems, so just let it go.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 lockfile.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/lockfile.c b/lockfile.c
index 931ebbd..0ade314 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -128,30 +128,25 @@ static void trim_last_path_elm(struct strbuf *path)
 static void resolve_symlink(struct strbuf *path)
 {
 	int depth = MAXDEPTH;
+	struct strbuf link;
+
+	strbuf_init(&link, path->len);
 
 	while (depth--) {
-		char link[PATH_MAX];
-		int link_len = readlink(path->buf, link, sizeof(link));
-		if (link_len < 0) {
-			/* not a symlink anymore */
-			return;
-		}
-		if (link_len >= sizeof(link)) {
-			warning("%s: symlink too long", path->buf);
-			return;
-		}
-		/* readlink() never null-terminates */
-		link[link_len] = '\0';
+		if (strbuf_readlink(&link, path->buf, path->len) < 0)
+			break;
 
-		if (is_absolute_path(link))
+		if (is_absolute_path(link.buf))
 			/* an absolute path replaces the whole path: */
 			strbuf_setlen(path, 0);
 		else
 			/* a relative path replaces the last element of path: */
 			trim_last_path_elm(path);
 
-		strbuf_add(path, link, link_len);
+		strbuf_addbuf(path, &link);
 	}
+
+	strbuf_release(&link);
 }
 
 /* We append ".lock" to the filename to derive the lockfile name: */
-- 
1.9.0