[PATCH] rebase -i -p: document shortcomings
- From
Jonathan Nieder <jrnieder@gmail.com>
- Date
- Jun 1, 2010, 01:43 UTC
- Message-ID
- <20100601014335.GA21970@progeny.tock>
The rebase --preserve-merges facility presents a list of commits in its instruction sheet and uses a separate table to keep track of their parents. Unfortunately, in practice this means that with -p after most attempts to rearrange patches, some commits have the "wrong" parent and the resulting history is rarely what the caller expected.
Yes, it would be nice to fix that. But first, add a warning to the manual to help the uninitiated understand what is going on.
Reported-by: Jiří Paleček <jpalecek@web.de> Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de> Cc: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> --- Pointers towards a real fix:
. http://thread.gmane.org/gmane.comp.version-control.git/79424/focus=79504 . http://thread.gmane.org/gmane.comp.version-control.git/77965/focus=80835 . http://thread.gmane.org/gmane.comp.version-control.git/131921/focus=132679 . http://repo.or.cz/w/git/price.git . http://repo.or.cz/w/git/dscho.git/shortlog/refs/heads/rebase-i-p
Thanks to all who have worked on this before.
Thoughts?
Documentation/git-rebase.txt | 26 ++++++++++++++++++++++++++ t/t3404-rebase-interactive.sh | 6 ++++++ 2 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt index 5863dec..330e9ea 100644 --- a/Documentation/git-rebase.txt +++ b/Documentation/git-rebase.txt @@ -306,6 +306,11 @@ link:howto/revert-a-faulty-merge.txt[revert-a-faulty-merge How-To] for details). -p:: --preserve-merges:: Instead of ignoring merges, try to recreate them. ++ +This uses the `--interactive` machinery internally, but combining it +with the `--interactive` option explicitly is generally not a good +idea (see BUGS below). + --root:: Rebase all commits reachable from <branch>, instead of @@ -607,6 +612,27 @@ The ripple effect of a "hard case" recovery is especially bad: case" recovery too! +BUGS +---- +The instruction sheet presented by `--preserve-merges --interactive` +does not represent the topology of the revision graph. Attempts to +reorder it tend to produce counterintuitive results. + +For example, an attempt to rearrange +------------ +1 --- 2 --- 3 --- 4 --- 5 +------------ +to +------------ +1 --- 2 --- 4 --- 3 --- 5 +------------ +by moving the "pick 4" line will result in the following history: +------------ + 3 + / +1 --- 2 --- 4 --- 5 +------------ + Authors ------ Written by Junio C Hamano <gitster@pobox.com> and diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh index f20ea38..6668907 100755 --- a/t/t3404-rebase-interactive.sh +++ b/t/t3404-rebase-interactive.sh @@ -181,6 +181,12 @@ test_expect_success '-p handles "no changes" gracefully' ' test $HEAD = $(git rev-parse HEAD) ' +test_expect_failure 'exchange two commits with -p' ' + FAKE_LINES="2 1" git rebase -i -p HEAD~2 && + test H = $(git cat-file commit HEAD^ | sed -ne \$p) && + test G = $(git cat-file commit HEAD | sed -ne \$p) +' + test_expect_success 'preserve merges with -p' ' git checkout -b to-be-preserved master^ && : > unrelated-file &&
-- 1.7.1