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[0/4,RFC] merge --autostash: apply autostash in more cases

Message ID pull.1002.git.1627042470.gitgitgadget@gmail.com (mailing list archive)
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Series merge --autostash: apply autostash in more cases | expand

Message

Lessley Dennington via GitGitGadget July 23, 2021, 12:14 p.m. UTC
This series aims to apply the stash created by 'git merge --autostash' in 2
situations that were not covered by the code:

 1. If the merge is fast-forward but the fast-forward operation fails -
    PATCH 3/4
 2. If the merge strategy completely fails to handle the merge (exit code 2)
    - PATCH 4/4

The first 2 commits are small improvements that I noticed while implementing
the other two.

I'm marking it [RFC] because I'm not 100% sure that trying to apply the
autostash in 3/4 and 4/4 is actually the best course of action (or if it
would be better to call 'save_autostash' instead). That's because:

For 3/4 (fast-forward fails): I'm not sure if 'unpack_trees' (called by
'checkout_fast_forward') is guaranteed to fail atomically, or it might fail
mid-way and leave the worktree unclean, in which case it might be better not
to apply the autostash, but just save it instead (and tell the user). In the
test case I'm adding, it does fail before starting to update the working
tree, but I'm not sure if it's always the case.

For 4/4 (merge strategy fails): Same reasoning: I'm not sure if all
strategies (and even less user-supplied ones, which are not documented but
kind of supported) are guaranteed to 'exit 2' before messing up the working
tree.

Philippe Blain (4):
  merge: add missing word "strategy" to a message
  Documentation: define 'MERGE_AUTOSTASH'
  merge: apply autostash if fast-forward fails
  merge: apply autostash if merge strategy fails

 Documentation/merge-options.txt |  3 ++-
 builtin/merge.c                 |  4 +++-
 t/t7600-merge.sh                | 19 +++++++++++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)


base-commit: d486ca60a51c9cb1fe068803c3f540724e95e83a
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1002%2Fphil-blain%2Fmerge-autostash-ff-fails-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1002/phil-blain/merge-autostash-ff-fails-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1002

Comments

Felipe Contreras July 23, 2021, 4:10 p.m. UTC | #1
Philippe Blain via GitGitGadget wrote:
> This series aims to apply the stash created by 'git merge --autostash' in 2
> situations that were not covered by the code:
> 
>  1. If the merge is fast-forward but the fast-forward operation fails -
>     PATCH 3/4
>  2. If the merge strategy completely fails to handle the merge (exit code 2)
>     - PATCH 4/4
> 
> The first 2 commits are small improvements that I noticed while implementing
> the other two.
> 
> I'm marking it [RFC] because I'm not 100% sure that trying to apply the
> autostash in 3/4 and 4/4 is actually the best course of action (or if it
> would be better to call 'save_autostash' instead). That's because:
> 
> For 3/4 (fast-forward fails): I'm not sure if 'unpack_trees' (called by
> 'checkout_fast_forward') is guaranteed to fail atomically, or it might fail
> mid-way and leave the worktree unclean, in which case it might be better not
> to apply the autostash, but just save it instead (and tell the user). In the
> test case I'm adding, it does fail before starting to update the working
> tree, but I'm not sure if it's always the case.

I'm not familiar with unpack_trees, but sans that possibility the whole
series looks fine to me.