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In e6c06e87a2 (last-modified: fix bug when some paths remain unhandled,
2025-09-18), we have fixed a bug where under certain circumstances,
git-last-modified(1) would BUG because there's still some unhandled
paths. The fix claims that the root cause here is criss-cross merges,
and it adds a test case that seemingly exercises this.
Curiously, this test case fails on some systems because the actual
output does not match our expectations:
diff --git a/expect b/actual
index 5271607..bdc620e 100644
--- a/expect
--- b/actual
@@ -1,3 +1,3 @@
km3 a
-k2 k
+km2 k
1 file
error: last command exited with $?=1
not ok 15 - last-modified with subdir and criss-cross merge
The output we see is git-name-rev(1) with `--annotate-stdin`. What it
does is to take the output of git-last-modified(1), which contains
object IDs of the blamed commits, and convert those object IDs into the
names of the corresponding tags. Interestingly, we indeed have both "k2"
and "km2" as tags, and even more interestingly both of these tags point
to the same commit. So the output we get isn't _wrong_, as the tags are
ambiguous.
But why do both of these tags point to the same commit? "km2" really is
supposed to be a merge, but due to the way the test is constructed the
merge turns into a fast-forward merge. Which means that the resulting
commit-graph does not even contain a criss-cross merge in the first place!
A quick test though shows that the test indeed triggers the bug, so
the initial analysis that the behaviour is triggered by such merges
must be wrong.
And it is: seemingly, the issue isn't with criss-cross merges, but
rather with a graph where different files in the same directory were
modified on both sides of a merge.
Refactor the test so that we explicitly test for this specific situation
instead of mentioning the "criss-cross merge" red herring. As the test
is very specific to the actual layout of the repository we also adapt it
to use its own standalone repository.
Note that this requires us to drop the `test_when_finished` call in
`check_last_modified` because it's not supported to execute that
function in a subshell.
This refactoring also fixes the original tag ambiguity that caused us to
fail on some platforms.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The recently introduced new subcommand git-last-modified(1) runs into an
error in some scenarios. It then would exit with the message:
BUG: paths remaining beyond boundary in last-modified
This seems to happens for example when criss-cross merges are involved.
In that scenario, the function diff_tree_combined() gets called.
The function diff_tree_combined() copies the `struct diff_options` from
the input `struct rev_info` to override some flags. One flag is
`recursive`, which is always set to 1. This has been the case since the
inception of this function in af3feefa1d (diff-tree -c: show a merge
commit a bit more sensibly., 2006-01-24).
This behavior is incompatible with git-last-modified(1), when called
non-recursive (which is the default).
The last-modified machinery uses a hashmap for all the paths it wants to
get the last-modified commit for. Through log_tree_commit() the callback
mark_path() is called. The diff machinery uses diff_tree_combined()
internally, and due to it's recursive behavior the callback receives
entries inside subtrees, but not the subtree entries themselves. So a
directory is never expelled from the hashmap, and the BUG() statement
gets hit.
Because there are many callers calling into diff_tree_combined(), both
directly and indirectly, we cannot simply change it's behavior.
Instead, add a flag `no_recursive_diff_tree_combined` which supresses
the behavior of diff_tree_combined() to override `recursive` and set
this flag in builtin/last-modified.c.
Signed-off-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Similar to git-blame(1), introduce a new subcommand
git-last-modified(1). This command shows the most recent modification to
paths in a tree. It does so by expanding the tree at a given commit,
taking note of the current state of each path, and then walking
backwards through history looking for commits where each path changed
into its final commit ID.
Based-on-patch-by: Jeff King <peff@peff.net>
Improved-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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