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Which operations are safe to interrupt? What will be the result? No change? Partial but valid result? Messy result? With what consequences?

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https://launchpad.net/~stephane-gourichon-lpad 2016-11-05 11:10:42 +00:00 • committed by admin
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# Context
* Git annex does a lot under the hood: replace files with symlinks, check and adjust moved links, etc.
* Git annex allows to mix and match with plain git commands.
* Operations may be interrupted by signal (Ctrl-C), by network failure (especially in mobile situation), by power failure (laptop on battery).
Git itself is mostly transactional: most actions can be interrupted and everything looks like they were never started.
I'm confident that you Joey have an eye for details and do the safe thing. Yet parameters above open up for a lot of combinations, some of which might not actually do what's intended, or are perhaps safe only for someone who knows where *not* to put a foot.
# Example
For example, nearly 5 years ago you wrote about interrupted `git annex add`: in [git annex add crash and subsequent recovery](https://git-annex.branchable.com/forum/git_annex_add_crash_and_subsequent_recovery/)
> Thought I'd mention how to clean up from interrupting git annex add. When you do that, it doesn't get a chance to git add the files it's added (this is normally done at the end, or sometimes at points in the middle when you're adding a lot of files). Which is also why fsck, whereis, and unannex wouldn't operate on them, since they only deal with files in git.
> So the first step is to manually use git add on any symlinks.
> I've made git annex add recover when ran a second time.
# Questions
* Which operations are safe to interrupt? What will be the result? No change? Partial but valid result? Messy result? With what consequences?
* What operations should *not* be performed after an interrupted one?
For example, let's say I've started a `git annex sync`. While it works, I realize there are unwanted changes. If I interrupt what is the result? Can I safely use manual git commands to add or remove some files to index, make separated commits, then git sync again?
I'm using a v5 repository, indirect mode, mixed content. Is it different in v6? In direct mode? In mixed vs non-mixed content repository?
# Wish a dedicated page in git-annex documentation
IMHO this is an important, difficult and changing topic, which would deserve its own "when things go wrong" topic pages, like [fsck: when things go wrong](https://git-annex.branchable.com/walkthrough/fsck__58___when_things_go_wrong/) and [transferring files: When things go wrong](https://git-annex.branchable.com/walkthrough/transferring_files__58___When_things_go_wrong/).
Perhaps just starting with broad rules like "Commands foo and bar are ok, baz is mostly ok just repeat it" or "in any on-trivial case, do `git annex sync` last after you check twice that any necessary commit is done" would be very appreciated.
Thank you.