95 lines
2.4 KiB
Markdown
95 lines
2.4 KiB
Markdown
Below is a test case which shows a way that the git-annex branch
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can become corrupted and lose data, including location log records and
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uuid.log lines.
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At the end, a commit on the git-annex branch removes one of the 2 lines
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from the uuid.log; which should never happen.
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The actual problem occurs earlier, at the "push point". Here a repo is
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cloned from the main one, initialized (adding the last uuid.log line),
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and then pushed back to the main one. That push is a fast-forward, so is
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allowed to directly update the git-annex branch in the main repo:
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b884fe5..c497739 git-annex -> git-annex
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Now the git-annex branch has a change that is not reflected in
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`.git/annex/index`, so the next time a change is made, it's committed
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using the out of date index, which causes a reversion of the changes
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that were pushed to the branch.
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---
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## Thoughts
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This is essentially the same reason why git blocks pushes to the checked-out
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branch of a non-bare repository.
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This problem only affects workflows that involve pushing. Pulling workflows
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do not directly update the local git-annex branch, so avoid the problem.
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And while bare repos are pushed to, they rarely have changes made directly
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to their git-annex branches, so while I think the same problem could
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happen with pushing to a bare repo, it's unlikely.
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None of which is to say this is not a bad bug that needs to be comprehensively
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fixed.
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Probably git-annex needs to record which ref of the git-annex branch
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corresponds to its index, and if the branch is at a different ref,
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merge it into the index.
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> And now that's [[done]]. I managed to do it with very little slowdown.
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>
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> A side benefit is that users can now safely check out the git-annex
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> branch and commit changes to it, and git-annex will notice them.
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> Before, it was documented to ignore such changes.
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> --[[Joey]]
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---
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## Workaround
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Users who want to prevent this bug from occuring when pushing to their
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non-bare repositories can install this script as `.git/hooks/update`
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<pre>
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#!/bin/sh
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if [ "$1" = refs/heads/git-annex ]; then
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exit 1
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fi
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</pre>
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--[[Joey]]
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---
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## Test Case
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<pre>
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#!/bin/sh
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mkdir annextest
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cd annextest
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git init dir1
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cd dir1
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git annex init
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touch foo
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echo hi > bar
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git annex add
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git commit -m add
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cd ..
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git clone dir1 dir2
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cd dir2
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git annex init otherdir
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git annex get
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# push point
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git push
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cd ..
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cd dir1
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echo "before"
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git show git-annex:uuid.log
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git annex drop foo --force
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echo "after"
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git show git-annex:uuid.log
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</pre>
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