[PATCH 2/2] merge: avoid searching for strategies with fewer than 0 conflicts

From: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 21, 2022, 04:38 UTC
Message-ID: <5657a05e7635ecadbb8d2e41ad97fe19f3633fdd.1661056709.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1331.git.1661056709.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

builtin/merge.c has a loop over the specified strategies, where if they all fail with conflicts, it picks the one with the least number of conflicts.

In the codepath that finds a successful merge, if an automatic commit was wanted, the code breaks out of the above loop, which makes sense. However, if the user requested there be no automatic commit, the loop would continue looking for a "better" strategy. Since it had just found a strategy with 0 conflicts though, and it is not possible to have fewer than 0 conflicts, the continuing search is guaranteed to be futile.

While searching additional strategies won't cause problems other than wasting energy, it is wasteful. Avoid searching for other strategies with fewer than 0 conflicts.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/merge.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index b4253710d19..f04100ce0da 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1718,12 +1718,18 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		 */
 		if (ret < 2) {
 			if (!ret) {
-				if (option_commit) {
+				if (option_commit)
 					/* Automerge succeeded. */
 					automerge_was_ok = 1;
-					break;
-				}
-				merge_was_ok = 1;
+				else
+					/* Merge good, but let user commit */
+					merge_was_ok = 1;
+				/*
+				 * This strategy worked; no point in trying
+				 * another.
+				 */
+				best_strategy = wt_strategy;
+				break;
 			}
 			cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
 			if (best_cnt <= 0 || cnt <= best_cnt) {

-- 
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