builtin/push.c: use strbuf instead of manual allocation

The command line arguments given to "git push" are massaged into
a list of refspecs in set_refspecs() function. This was implemented
using xmalloc, strcpy and friends, but it is much easier to read if
done using strbuf.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/push.c

@@ -41,29 +41,22 @@ static void set_refspecs(const char **refs, int nr)
 	for (i = 0; i < nr; i++) {
 		const char *ref = refs[i];
 		if (!strcmp("tag", ref)) {
-			char *tag;
-			int len;
+			struct strbuf tagref = STRBUF_INIT;
 			if (nr <= ++i)
 				die(_("tag shorthand without <tag>"));
-			len = strlen(refs[i]) + 11;
-			if (deleterefs) {
-				tag = xmalloc(len+1);
-				strcpy(tag, ":refs/tags/");
-			} else {
-				tag = xmalloc(len);
-				strcpy(tag, "refs/tags/");
-			}
-			strcat(tag, refs[i]);
-			ref = tag;
-		} else if (deleterefs && !strchr(ref, ':')) {
-			char *delref;
-			int len = strlen(ref)+1;
-			delref = xmalloc(len+1);
-			strcpy(delref, ":");
-			strcat(delref, ref);
-			ref = delref;
-		} else if (deleterefs)
-			die(_("--delete only accepts plain target ref names"));
+			ref = refs[i];
+			if (deleterefs)
+				strbuf_addf(&tagref, ":refs/tags/%s", ref);
+			else
+				strbuf_addf(&tagref, "refs/tags/%s", ref);
+			ref = strbuf_detach(&tagref, NULL);
+		} else if (deleterefs) {
+			struct strbuf delref = STRBUF_INIT;
+			if (strchr(ref, ':'))
+				die(_("--delete only accepts plain target ref names"));
+			strbuf_addf(&delref, ":%s", ref);
+			ref = strbuf_detach(&delref, NULL);
+		}
 		add_refspec(ref);
 	}
 }