cocci: add and apply free_commit_list() rules

Add and apply coccinelle rules to remove "if (E)" before
"free_commit_list(E)", the function can accept NULL, and further
change cases where "E = NULL" followed to also be unconditionally.

The code changes in this commit were entirely made by the coccinelle
rule being added here, and applied with:

    make contrib/coccinelle/free.cocci.patch
    patch -p1 <contrib/coccinelle/free.cocci.patch

The only manual intervention here is that the the relevant code in
commit.c has been manually re-indented.

Suggested-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rev-list.c

@@ -213,10 +213,8 @@ static void show_commit(struct commit *commit, void *data)
 
 static void finish_commit(struct commit *commit)
 {
-	if (commit->parents) {
-		free_commit_list(commit->parents);
-		commit->parents = NULL;
-	}
+	free_commit_list(commit->parents);
+	commit->parents = NULL;
 	free_commit_buffer(the_repository->parsed_objects,
 			   commit);
 }

commit.c

@@ -397,17 +397,14 @@ int parse_commit_buffer(struct repository *r, struct commit *item, const void *b
 
 	if (item->object.parsed)
 		return 0;
-
-	if (item->parents) {
-		/*
-		 * Presumably this is leftover from an earlier failed parse;
-		 * clear it out in preparation for us re-parsing (we'll hit the
-		 * same error, but that's good, since it lets our caller know
-		 * the result cannot be trusted.
-		 */
-		free_commit_list(item->parents);
-		item->parents = NULL;
-	}
+	/*
+	 * Presumably this is leftover from an earlier failed parse;
+	 * clear it out in preparation for us re-parsing (we'll hit the
+	 * same error, but that's good, since it lets our caller know
+	 * the result cannot be trusted.
+	 */
+	free_commit_list(item->parents);
+	item->parents = NULL;
 
 	tail += size;
 	if (tail <= bufptr + tree_entry_len + 1 || memcmp(bufptr, "tree ", 5) ||

contrib/coccinelle/free.cocci

@@ -2,13 +2,21 @@
 expression E;
 @@
 - if (E)
+(
   free(E);
+|
+  free_commit_list(E);
+)
 
 @@
 expression E;
 @@
 - if (!E)
+(
   free(E);
+|
+  free_commit_list(E);
+)
 
 @@
 expression E;
@@ -16,3 +24,22 @@ expression E;
 - free(E);
 + FREE_AND_NULL(E);
 - E = NULL;
+
+@@
+expression E;
+@@
+- if (E)
+- {
+  free_commit_list(E);
+  E = NULL;
+- }
+
+@@
+expression E;
+statement S;
+@@
+- if (E) {
++ if (E)
+  S
+  free_commit_list(E);
+- }

revision.c

@@ -1456,10 +1456,9 @@ static int limit_list(struct rev_info *revs)
 	if (revs->left_only || revs->right_only)
 		limit_left_right(newlist, revs);
 
-	if (bottom) {
+	if (bottom)
 		limit_to_ancestry(bottom, newlist);
-		free_commit_list(bottom);
-	}
+	free_commit_list(bottom);
 
 	/*
 	 * Check if any commits have become TREESAME by some of their parents
@@ -4080,10 +4079,8 @@ static void create_boundary_commit_list(struct rev_info *revs)
 	 * boundary commits anyway.  (This is what the code has always
 	 * done.)
 	 */
-	if (revs->commits) {
-		free_commit_list(revs->commits);
-		revs->commits = NULL;
-	}
+	free_commit_list(revs->commits);
+	revs->commits = NULL;
 
 	/*
 	 * Put all of the actual boundary commits from revs->boundary_commits
@@ -4220,10 +4217,8 @@ struct commit *get_revision(struct rev_info *revs)
 		graph_update(revs->graph, c);
 	if (!c) {
 		free_saved_parents(revs);
-		if (revs->previous_parents) {
-			free_commit_list(revs->previous_parents);
-			revs->previous_parents = NULL;
-		}
+		free_commit_list(revs->previous_parents);
+		revs->previous_parents = NULL;
 	}
 	return c;
 }

submodule.c

@@ -664,8 +664,7 @@ void show_submodule_diff_summary(struct diff_options *o, const char *path,
 	print_submodule_diff_summary(sub, &rev, o);
 
 out:
-	if (merge_bases)
-		free_commit_list(merge_bases);
+	free_commit_list(merge_bases);
 	clear_commit_marks(left, ~0);
 	clear_commit_marks(right, ~0);
 	if (sub) {
@@ -754,8 +753,7 @@ void show_submodule_inline_diff(struct diff_options *o, const char *path,
 
 done:
 	strbuf_release(&sb);
-	if (merge_bases)
-		free_commit_list(merge_bases);
+	free_commit_list(merge_bases);
 	if (left)
 		clear_commit_marks(left, ~0);
 	if (right)