transport: use strbufs for status table "quickref" strings

We generate range strings like "1234abcd...5678efab" for use
in the the fetch and push status tables. We use fixed-size
buffers along with strcat to do so. These aren't buggy, as
our manual size computation is correct, but there's nothing
checking that this is so.  Let's switch them to strbufs
instead, which are obviously correct, and make it easier to
audit the code base for problematic calls to strcat().

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 19 insertions, 16 deletions

diff --git a/builtin/fetch.c b/builtin/fetch.c
index 470372552..841880ec2 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -528,36 +528,38 @@ static int update_local_ref(struct ref *ref,
 	}
 
 	if (in_merge_bases(current, updated)) {
-		char quickref[83];
+		struct strbuf quickref = STRBUF_INIT;
 		int r;
-		strcpy(quickref, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));
-		strcat(quickref, "..");
-		strcat(quickref, find_unique_abbrev(ref->new_sha1, DEFAULT_ABBREV));
+		strbuf_add_unique_abbrev(&quickref, current->object.sha1, DEFAULT_ABBREV);
+		strbuf_addstr(&quickref, "..");
+		strbuf_add_unique_abbrev(&quickref, ref->new_sha1, DEFAULT_ABBREV);
 		if ((recurse_submodules != RECURSE_SUBMODULES_OFF) &&
 		    (recurse_submodules != RECURSE_SUBMODULES_ON))
 			check_for_new_submodule_commits(ref->new_sha1);
 		r = s_update_ref("fast-forward", ref, 1);
 		strbuf_addf(display, "%c %-*s %-*s -> %s%s",
 			    r ? '!' : ' ',
-			    TRANSPORT_SUMMARY_WIDTH, quickref,
+			    TRANSPORT_SUMMARY_WIDTH, quickref.buf,
 			    REFCOL_WIDTH, remote, pretty_ref,
 			    r ? _("  (unable to update local ref)") : "");
+		strbuf_release(&quickref);
 		return r;
 	} else if (force || ref->force) {
-		char quickref[84];
+		struct strbuf quickref = STRBUF_INIT;
 		int r;
-		strcpy(quickref, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));
-		strcat(quickref, "...");
-		strcat(quickref, find_unique_abbrev(ref->new_sha1, DEFAULT_ABBREV));
+		strbuf_add_unique_abbrev(&quickref, current->object.sha1, DEFAULT_ABBREV);
+		strbuf_addstr(&quickref, "...");
+		strbuf_add_unique_abbrev(&quickref, ref->new_sha1, DEFAULT_ABBREV);
 		if ((recurse_submodules != RECURSE_SUBMODULES_OFF) &&
 		    (recurse_submodules != RECURSE_SUBMODULES_ON))
 			check_for_new_submodule_commits(ref->new_sha1);
 		r = s_update_ref("forced-update", ref, 1);
 		strbuf_addf(display, "%c %-*s %-*s -> %s  (%s)",
 			    r ? '!' : '+',
-			    TRANSPORT_SUMMARY_WIDTH, quickref,
+			    TRANSPORT_SUMMARY_WIDTH, quickref.buf,
 			    REFCOL_WIDTH, remote, pretty_ref,
 			    r ? _("unable to update local ref") : _("forced update"));
+		strbuf_release(&quickref);
 		return r;
 	} else {
 		strbuf_addf(display, "! %-*s %-*s -> %s  %s",
diff --git a/transport.c b/transport.c
index 2d51348f3..3b47d493d 100644
--- a/transport.c
+++ b/transport.c
@@ -654,23 +654,24 @@ static void print_ok_ref_status(struct ref *ref, int porcelain)
 			"[new branch]"),
 			ref, ref->peer_ref, NULL, porcelain);
 	else {
-		char quickref[84];
+		struct strbuf quickref = STRBUF_INIT;
 		char type;
 		const char *msg;
 
-		strcpy(quickref, status_abbrev(ref->old_sha1));
+		strbuf_addstr(&quickref, status_abbrev(ref->old_sha1));
 		if (ref->forced_update) {
-			strcat(quickref, "...");
+			strbuf_addstr(&quickref, "...");
 			type = '+';
 			msg = "forced update";
 		} else {
-			strcat(quickref, "..");
+			strbuf_addstr(&quickref, "..");
 			type = ' ';
 			msg = NULL;
 		}
-		strcat(quickref, status_abbrev(ref->new_sha1));
+		strbuf_addstr(&quickref, status_abbrev(ref->new_sha1));
 
-		print_ref_status(type, quickref, ref, ref->peer_ref, msg, porcelain);
+		print_ref_status(type, quickref.buf, ref, ref->peer_ref, msg, porcelain);
+		strbuf_release(&quickref);
 	}
 }