Revert "name-rev: release unused name strings"

This reverts commit 2d53975.

3656f84 (name-rev: prefer shorter names over following merges,
2021-12-04) broke the assumption of 2d53975 (name-rev: release unused
name strings, 2020-02-04) that a better name for a child is a better
name for all of its ancestors as well, because it added a penalty for
generation > 0.  This leads to strings being free(3)'d that are still
needed.

079f970 (name-rev: sort tip names before applying, 2020-02-05)
already reduced the number of free(3) calls for the use case that
motivated the original patch (name-rev --all in the Chromium repository)
from ca. 44000 to 5, and 3656f84 eliminated even those few.  So this
revert won't affect name-rev's performance on that particular repo.

Reported-by: Thomas Hurst <[email protected]>
Helped-by: Elijah Newren <[email protected]>
Signed-off-by: René Scharfe <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rscharfe

builtin/name-rev.c

@@ -17,7 +17,7 @@
 #define CUTOFF_DATE_SLOP 86400
 
 struct rev_name {
-	char *tip_name;
+	const char *tip_name;
 	timestamp_t taggerdate;
 	int generation;
 	int distance;
@@ -34,7 +34,7 @@ static struct commit_rev_name rev_names;
 
 static int is_valid_rev_name(const struct rev_name *name)
 {
-	return name && (name->generation || name->tip_name);
+	return name && name->tip_name;
 }
 
 static struct rev_name *get_commit_rev_name(const struct commit *commit)
@@ -96,20 +96,9 @@ static struct rev_name *create_or_update_name(struct commit *commit,
 {
 	struct rev_name *name = commit_rev_name_at(&rev_names, commit);
 
-	if (is_valid_rev_name(name)) {
-		if (!is_better_name(name, taggerdate, generation, distance, from_tag))
-			return NULL;
-
-		/*
-		 * This string might still be shared with ancestors
-		 * (generation > 0).  We can release it here regardless,
-		 * because the new name that has just won will be better
-		 * for them as well, so name_rev() will replace these
-		 * stale pointers when it processes the parents.
-		 */
-		if (!name->generation)
-			free(name->tip_name);
-	}
+	if (is_valid_rev_name(name) &&
+	    !is_better_name(name, taggerdate, generation, distance, from_tag))
+		return NULL;
 
 	name->taggerdate = taggerdate;
 	name->generation = generation;