Subject: [PATCH v2] sequencer.c: use reverse_commit_list() helper

From: "Jayati Shrivastava via GitGitGadget" <[email-masked]>
Date: Wed, 16 Mar 2022 10:42:36 +0000

From: Jayati Shrivastava <[email-masked]>

Instead of creating a new allocation, reverse the original
list in-place by calling the reverse_commit_list() helper.
The original code discards the list "bases" after storing
its reverse copy in a newly created list "reversed". If the
code that followed from here used both "bases" and "reversed",
the modification would not have worked, but since the original
list "bases" gets discarded, we can simply reverse "bases"
in-place with the reverse_commit_list() helper and reuse the
same variable in the code that follows.

Signed-off-by: Jayati Shrivastava <[email-masked]>
---
    Use reverse_commit_list helper function for in-place list reversal
    
    This patch addresses https://github.com/gitgitgadget/git/issues/1156 . I
    have left builtin/merge.c unmodified since in its case, the original
    list is needed separately from the reverse copy.
    
    (Please excuse if you are receiving this patch again. I had previously
    sent it using git send-email but for some reason the patches are not
    getting delivered to the mailing list despite correctly passing the
    --to/--cc/--in-reply-to options.)

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1177%2Fvictorphoenix3%2Freverse-list-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1177/victorphoenix3/reverse-list-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1177

Range-diff vs v1:

 1:  8c3c6c9ed4c ! 1:  f794bcd8bda Use reverse_commit_list helper function for in-place list reversal
     @@
       ## Metadata ##
     -Author: JAYATI SHRIVASTAVA <[email-masked]>
     +Author: Jayati Shrivastava <[email-masked]>
      
       ## Commit message ##
     -    Use reverse_commit_list helper function for in-place list reversal
     +    sequencer.c: use reverse_commit_list() helper
      
     -    Here, a reverse copy of a list is being created by iterating
     -    over the list after which the original list is discarded.
     -    Instead of creating a new allocation, we can reverse the
     -    original list in-place using the reverse_commit_list helper
     -    function.
     +    Instead of creating a new allocation, reverse the original
     +    list in-place by calling the reverse_commit_list() helper.
     +    The original code discards the list "bases" after storing
     +    its reverse copy in a newly created list "reversed". If the
     +    code that followed from here used both "bases" and "reversed",
     +    the modification would not have worked, but since the original
     +    list "bases" gets discarded, we can simply reverse "bases"
     +    in-place with the reverse_commit_list() helper and reuse the
     +    same variable in the code that follows.
      
          Signed-off-by: Jayati Shrivastava <[email-masked]>

 sequencer.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 35006c0cea6..bccbb9e3522 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3749,7 +3749,7 @@ static int do_merge(struct repository *r,
 	int run_commit_flags = 0;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct commit *head_commit, *merge_commit, *i;
-	struct commit_list *bases, *j, *reversed = NULL;
+	struct commit_list *bases, *j;
 	struct commit_list *to_merge = NULL, **tail = &to_merge;
 	const char *strategy = !opts->xopts_nr &&
 		(!opts->strategy ||
@@ -3984,9 +3984,7 @@ static int do_merge(struct repository *r,
 		      git_path_merge_head(r), 0);
 	write_message("no-ff", 5, git_path_merge_mode(r), 0);
 
-	for (j = bases; j; j = j->next)
-		commit_list_insert(j->item, &reversed);
-	free_commit_list(bases);
+	bases = reverse_commit_list(bases);
 
 	repo_read_index(r);
 	init_merge_options(&o, r);
@@ -4002,10 +4000,10 @@ static int do_merge(struct repository *r,
 		 * update the index and working copy immediately.
 		 */
 		ret = merge_ort_recursive(&o,
-					  head_commit, merge_commit, reversed,
+					  head_commit, merge_commit, bases,
 					  &i);
 	} else {
-		ret = merge_recursive(&o, head_commit, merge_commit, reversed,
+		ret = merge_recursive(&o, head_commit, merge_commit, bases,
 				      &i);
 	}
 	if (ret <= 0)

base-commit: b896f729e240d250cf56899e6a0073f6aa469f5d
-- 
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