submodule--helper: refactor "errmsg_str" to be a "struct strbuf"

Refactor code added in e83e3333b57 (submodule: port submodule
subcommand 'summary' from shell to C, 2020-08-13) so that "errmsg" and
"errmsg_str" are folded into one. The distinction between the empty
string and NULL is something that's tested for by
e.g. "t/t7401-submodule-summary.sh".

This is in preparation for fixing a memory leak the "struct strbuf" in
the pre-image.

Let's also pass a "const char *" to print_submodule_summary(), as it
should not be modifying the "errmsg".

Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Reviewed-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 7e70f4954702f90a17a84f40190113b227577446..befcd2d0d961bff18c20f02ea1885677a7a0c08a 100644 (file)
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -761,7 +761,7 @@ static char *verify_submodule_committish(const char *sm_path,
        return strbuf_detach(&result, NULL);
 }
 
-static void print_submodule_summary(struct summary_cb *info, char *errmsg,
+static void print_submodule_summary(struct summary_cb *info, const char *errmsg,
                                    int total_commits, const char *displaypath,
                                    const char *src_abbrev, const char *dst_abbrev,
                                    struct module_cb *p)
@@ -819,7 +819,7 @@ static void generate_submodule_summary(struct summary_cb *info,
 {
        char *displaypath, *src_abbrev = NULL, *dst_abbrev;
        int missing_src = 0, missing_dst = 0;
-       char *errmsg = NULL;
+       struct strbuf errmsg = STRBUF_INIT;
        int total_commits = -1;
 
        if (!info->cached && oideq(&p->oid_dst, null_oid())) {
@@ -920,23 +920,21 @@ static void generate_submodule_summary(struct summary_cb *info,
                 * submodule, i.e., deleted or changed to blob
                 */
                if (S_ISGITLINK(p->mod_dst)) {
-                       struct strbuf errmsg_str = STRBUF_INIT;
                        if (missing_src && missing_dst) {
-                               strbuf_addf(&errmsg_str, "  Warn: %s doesn't contain commits %s and %s\n",
+                               strbuf_addf(&errmsg, "  Warn: %s doesn't contain commits %s and %s\n",
                                            displaypath, oid_to_hex(&p->oid_src),
                                            oid_to_hex(&p->oid_dst));
                        } else {
-                               strbuf_addf(&errmsg_str, "  Warn: %s doesn't contain commit %s\n",
+                               strbuf_addf(&errmsg, "  Warn: %s doesn't contain commit %s\n",
                                            displaypath, missing_src ?
                                            oid_to_hex(&p->oid_src) :
                                            oid_to_hex(&p->oid_dst));
                        }
-                       errmsg = strbuf_detach(&errmsg_str, NULL);
                }
        }
 
-       print_submodule_summary(info, errmsg, total_commits,
-                               displaypath, src_abbrev,
+       print_submodule_summary(info, errmsg.len ? errmsg.buf : NULL,
+                               total_commits, displaypath, src_abbrev,
                                dst_abbrev, p);
 
        free(displaypath);