submodule-config: passing name reference for .gitmodule blobs

Commit 959b5455 (submodule: implement a config API for lookup of
.gitmodules values, 2015-08-18) implemented the initial version of the
submodule config cache. During development of that initial version we
extracted the function gitmodule_sha1_from_commit(). During that process
we missed that the strbuf rev was still used in config_from() and now is
left empty. Lets fix this by also returning this string.

This means that now when reading .gitmodules from revisions, the error
messages also contain a reference to the blob they are from.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule-config.c

@@ -349,9 +349,9 @@ static int parse_config(const char *var, const char *value, void *data)
 }
 
 static int gitmodule_sha1_from_commit(const unsigned char *commit_sha1,
-				      unsigned char *gitmodules_sha1)
+				      unsigned char *gitmodules_sha1,
+				      struct strbuf *rev)
 {
-	struct strbuf rev = STRBUF_INIT;
 	int ret = 0;
 
 	if (is_null_sha1(commit_sha1)) {
@@ -359,11 +359,10 @@ static int gitmodule_sha1_from_commit(const unsigned char *commit_sha1,
 		return 1;
 	}
 
-	strbuf_addf(&rev, "%s:.gitmodules", sha1_to_hex(commit_sha1));
-	if (get_sha1(rev.buf, gitmodules_sha1) >= 0)
+	strbuf_addf(rev, "%s:.gitmodules", sha1_to_hex(commit_sha1));
+	if (get_sha1(rev->buf, gitmodules_sha1) >= 0)
 		ret = 1;
 
-	strbuf_release(&rev);
 	return ret;
 }
 
@@ -375,6 +374,7 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 		const unsigned char *commit_sha1, const char *key,
 		enum lookup_type lookup_type)
 {
+	struct strbuf rev = STRBUF_INIT;
 	unsigned long config_size;
 	char *config;
 	unsigned char sha1[20];
@@ -397,8 +397,10 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 		return entry->config;
 	}
 
-	if (!gitmodule_sha1_from_commit(commit_sha1, sha1))
+	if (!gitmodule_sha1_from_commit(commit_sha1, sha1, &rev)) {
+		strbuf_release(&rev);
 		return NULL;
+	}
 
 	switch (lookup_type) {
 	case lookup_name:
@@ -408,14 +410,19 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 		submodule = cache_lookup_path(cache, sha1, key);
 		break;
 	}
-	if (submodule)
+	if (submodule) {
+		strbuf_release(&rev);
 		return submodule;
+	}
 
 	config = read_sha1_file(sha1, &type, &config_size);
-	if (!config)
+	if (!config) {
+		strbuf_release(&rev);
 		return NULL;
+	}
 
 	if (type != OBJ_BLOB) {
+		strbuf_release(&rev);
 		free(config);
 		return NULL;
 	}
@@ -425,8 +432,9 @@ static const struct submodule *config_from(struct submodule_cache *cache,
 	parameter.commit_sha1 = commit_sha1;
 	parameter.gitmodules_sha1 = sha1;
 	parameter.overwrite = 0;
-	git_config_from_mem(parse_config, "submodule-blob", "",
+	git_config_from_mem(parse_config, "submodule-blob", rev.buf,
 			config, config_size, &parameter);
+	strbuf_release(&rev);
 	free(config);
 
 	switch (lookup_type) {

t/t7411-submodule-config.sh

@@ -82,6 +82,17 @@ test_expect_success 'error in one submodule config lets continue' '
 	)
 '
 
+test_expect_success 'error message contains blob reference' '
+	(cd super &&
+		sha1=$(git rev-parse HEAD) &&
+		test-submodule-config \
+			HEAD b \
+			HEAD submodule \
+				2>actual_err &&
+		grep "submodule-blob $sha1:.gitmodules" actual_err >/dev/null
+	)
+'
+
 cat >super/expect_url <<EOF
 Submodule url: 'git@somewhere.else.net:a.git' for path 'b'
 Submodule url: 'git@somewhere.else.net:submodule.git' for path 'submodule'