use strbuf_add_unique_abbrev() for adding short hashes, part 2

Call strbuf_add_unique_abbrev() to add abbreviated hashes to strbufs
instead of taking detours through find_unique_abbrev() and its static
buffer.  This is shorter and a bit more efficient.

1eb47f167d already converted six cases,
this patch covers three more.

A semantic patch for Coccinelle is included for easier checking for
new cases that might be introduced in the future.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/coccinelle/strbuf.cocci

@@ -9,3 +9,9 @@ expression E1, E2;
 @@
 - strbuf_addf(E1, "%s", E2);
 + strbuf_addstr(E1, E2);
+
+@@
+expression E1, E2, E3;
+@@
+- strbuf_addstr(E1, find_unique_abbrev(E2, E3));
++ strbuf_add_unique_abbrev(E1, E2, E3);

diff.c

@@ -3086,7 +3086,7 @@ static void fill_metainfo(struct strbuf *msg,
 		}
 		strbuf_addf(msg, "%s%sindex %s..", line_prefix, set,
 			    find_unique_abbrev(one->oid.hash, abbrev));
-		strbuf_addstr(msg, find_unique_abbrev(two->oid.hash, abbrev));
+		strbuf_add_unique_abbrev(msg, two->oid.hash, abbrev);
 		if (one->mode == two->mode)
 			strbuf_addf(msg, " %06o", one->mode);
 		strbuf_addf(msg, "%s\n", reset);

submodule.c

@@ -374,7 +374,7 @@ void show_submodule_summary(FILE *f, const char *path,
 			find_unique_abbrev(one, DEFAULT_ABBREV));
 	if (!fast_backward && !fast_forward)
 		strbuf_addch(&sb, '.');
-	strbuf_addstr(&sb, find_unique_abbrev(two, DEFAULT_ABBREV));
+	strbuf_add_unique_abbrev(&sb, two, DEFAULT_ABBREV);
 	if (message)
 		strbuf_addf(&sb, " %s%s\n", message, reset);
 	else

wt-status.c

@@ -1326,8 +1326,7 @@ static int grab_1st_switch(unsigned char *osha1, unsigned char *nsha1,
 	if (!strcmp(cb->buf.buf, "HEAD")) {
 		/* HEAD is relative. Resolve it to the right reflog entry. */
 		strbuf_reset(&cb->buf);
-		strbuf_addstr(&cb->buf,
+		strbuf_add_unique_abbrev(&cb->buf, nsha1, DEFAULT_ABBREV);
-			      find_unique_abbrev(nsha1, DEFAULT_ABBREV));
 	}
 	return 1;
 }