merge-ort: allow rename detection to be disabled

When merge-ort was written, I did not at first allow rename detection to
be disabled, because I suspected that most folks disabling rename
detection were doing so solely for performance reasons.  Since I put a
lot of working into providing dramatic speedups for rename detection
performance as used by the merge machinery, I wanted to know if there
were still real world repositories where rename detection was
problematic from a performance perspective.  We have had years now to
collect such information, and while we never received one, waiting
longer with the option disabled seems unlikely to help surface such
issues at this point.  Also, there has been at least one request to
allow rename detection to be disabled for behavioral rather than
performance reasons (see the thread including
https://lore.kernel.org/git/CABPp-BG-Nx6SCxxkGXn_Fwd2wseifMFND8eddvWxiZVZk0zRaA@mail.gmail.com/
), so let's start heeding the config and command line settings.

Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/merge-strategies.adoc b/Documentation/merge-strategies.adoc
index 93822ebc4e83b0abf10583d822a8d40bd50b86d7..59f5ae36ccb1dd52ec6e36e7776e980fde24b1a4 100644 (file)
--- a/Documentation/merge-strategies.adoc
+++ b/Documentation/merge-strategies.adoc
@@ -82,6 +82,11 @@ find-renames[=<n>];;
 rename-threshold=<n>;;
        Deprecated synonym for `find-renames=<n>`.
 
+no-renames;;
+       Turn off rename detection. This overrides the `merge.renames`
+       configuration variable.
+       See also linkgit:git-diff[1] `--no-renames`.
+
 subtree[=<path>];;
        This option is a more advanced form of 'subtree' strategy, where
        the strategy makes a guess on how two trees must be shifted to
@@ -107,7 +112,7 @@ For a path that is a submodule, the same caution as 'ort' applies to this
 strategy.
 +
 The 'recursive' strategy takes the same options as 'ort'.  However,
-there are three additional options that 'ort' ignores (not documented
+there are two additional options that 'ort' ignores (not documented
 above) that are potentially useful with the 'recursive' strategy:
 
 patience;;
@@ -121,11 +126,6 @@ diff-algorithm=[patience|minimal|histogram|myers];;
        specifically uses `diff-algorithm=histogram`, while `recursive`
        defaults to the `diff.algorithm` config setting.
 
-no-renames;;
-       Turn off rename detection. This overrides the `merge.renames`
-       configuration variable.
-       See also linkgit:git-diff[1] `--no-renames`.
-
 resolve::
        This can only resolve two heads (i.e. the current branch
        and another branch you pulled from) using a 3-way merge

diff --git a/merge-ort.c b/merge-ort.c
index b4ff24403a11634747e0df4234de21e0c2730010..1d3b690224ef7617d8b26dca29d3ea5685a93af0 100644 (file)
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -3448,6 +3448,11 @@ static int detect_and_process_renames(struct merge_options *opt)
 
        if (!possible_renames(renames))
                goto cleanup;
+       if (!opt->detect_renames) {
+               renames->redo_after_renames = 0;
+               renames->cached_pairs_valid_side = 0;
+               goto cleanup;
+       }
 
        trace2_region_enter("merge", "regular renames", opt->repo);
        detection_run |= detect_regular_renames(opt, MERGE_SIDE1);

diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
index eea19907b550c4a97a7ca7760f1be30bea7d8db0..44f7d0775933f2e3a75cd52fc12897ab34748946 100755 (executable)
--- a/t/t4301-merge-tree-write-tree.sh
+++ b/t/t4301-merge-tree-write-tree.sh
@@ -73,6 +73,12 @@ test_expect_success 'Clean merge' '
        test_cmp expect actual
 '
 
+# Repeat the previous test, but turn off rename detection
+test_expect_success 'Failed merge without rename detection' '
+       test_must_fail git -c diff.renames=false merge-tree --write-tree side1 side3 >out &&
+       grep "CONFLICT (modify/delete): numbers deleted" out
+'
+
 test_expect_success 'Content merge and a few conflicts' '
        git checkout side1^0 &&
        test_must_fail git merge side2 &&