Re: [BUG] git-log: tracking deleted file in a repository with multiple "initial commit" histories

From: Brian Norris <computersforpeace@gmail.com>
Date: Feb 18, 2016, 22:27 UTC
Message-ID: <20160218222713.GA50021@google.com>
In-Reply-To: <20160216222942.GA9014@sigill.intra.peff.net>

On Tue, Feb 16, 2016 at 05:29:42PM -0500, Jeff King wrote:

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> On Tue, Feb 16, 2016 at 01:24:29PM -0800, Brian Norris wrote:
> 
> > On Tue, Feb 16, 2016 at 03:45:57PM -0500, Jeff King wrote:
> > > See the section on History Simplification in git-log. But basically,
> > > when you specify a pathspec, git does not traverse side branches that
> > > had no effect on the given pathspec.
> > 
> > Thanks for the pointer. Is this done primarily for performance reasons,
> > or for UI simplicity (e.g., to avoid some kinds of double-counting)?
> > Seems like it generates unintuitive behaviors, but if it's helping block
> > other unintuitive behaviors, then maybe it can't be resolved easily.
> 
> Both, I think. Try looking at "--full-history" and you will see that it
> has a lot of cruft that is probably not that interesting. But

I wasn't seeing the "cruft" at first, but now I see. It appears, BTW, that 'git log --full-history -- <path>' gives vastly different commits than 'git log --full-history --graph -- <path>'. (The latter has a lot more "cruft" about unrelated merges.) That seems like a weird inconsistency...

> simplifying further (e.g., with "--simplify-merges") doesn't tell much
> of the whole story (or maybe it does; we do see the final deletion
> there, which is the end state).

git log --full-history --simplify-merges -- init/iptables.conf and git log --full-history --simplify-merges --graph --oneline -- init/iptables.conf

give good results for me, showing every commit that actually modifies the file, AFAICT.

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> > FWIW, I quite often use git-log to look at the history of a deleted
> > file. Seems like a pretty big hole if the default behavior is going to
> > prune away the entire history of the file.
> 
> It doesn't normally.

That doesn't really change my statement.

> What happened is that you had two parallel
> histories, and the final state of the file could be explained by
> following the simpler of the two histories (the one where it never
> existed in the first place).

I (sort of) understand what happened. But I disagree that it's a good default. It's obviously not what the user is asking for.

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> > > If you want to see the full history, you can with "--full-history"
> > > (there are some other simplification possibilities, but I don't think
> > > any of them are interesting for your particular case).
> > 
> > --full-history gives me what I want (I'll admit, I didn't read through
> > all the other "History Simplification" documentation). Can I make this
> > the default somehow?
> 
> No, but you can make an alias that includes it.

Sure.

Thanks for the help!

Brian