Re: weird behaviour in git

From: Thomas Klausner <tk@giga.or.at>
Date: Feb 26, 2015, 14:58 UTC
Message-ID: <20150226145848.GQ19896@danbala.tuwien.ac.at>
In-Reply-To: <54EF3179.8030104@drmicha.warpmail.net>

On Thu, Feb 26, 2015 at 03:45:13PM +0100, Michael J Gruber wrote:

Show 56 quoted lines

> Thomas Klausner venit, vidit, dixit 26.02.2015 15:12:
> > Hi!
> > 
> > I've played around with git and found that 'git mv' does not honor
> > what I tell it to do:
> > 
> > wiz@yt:~> mkdir a
> > wiz@yt:~> cd a
> > wiz@yt:~/a> git init .
> > Initialized empty Git repository in /home/wiz/a/.git/
> > wiz@yt:~/a> touch a
> > wiz@yt:~/a> git add a
> > wiz@yt:~/a> git commit -m 'add a'
> > [master (root-commit) 99d0ee7] add a
> >  1 file changed, 0 insertions(+), 0 deletions(-)
> >  create mode 100644 a
> > wiz@yt:~/a> git mv a b
> > wiz@yt:~/a> touch Makefile
> > wiz@yt:~/a> git add Makefile
> > wiz@yt:~/a> git commit
> > 
> > 
> > # Please enter the commit message for your changes. Lines starting
> > # with '#' will be ignored, and an empty message aborts the commit.
> > # On branch master
> > # Changes to be committed:
> > #       renamed:    a -> Makefile
> > #       new file:   b
> > #
> > 
> > This is reproducible for me with "git version 2.3.0" on
> > NetBSD-7.99.5/amd64.
> > 
> > I guess this happens because the checksums of the files are the same
> > and 'Makefile' is earlier when sorting, but since I explicitly told
> > "git mv" old and new name, I think that's a bug nevertheless.
> >  Thomas
> > 
> 
> git tracks content, not paths.
> 
> It does record the path at which the tracked content is, of course. But
> it tracks the history of content, not that of paths.
> 
> What you see in the diff above is merely one way to interpret the
> history of the content. Saying
> 
> renamed:  a -> b
> new file: Makefile
> 
> leads to the same content at the same paths (with the proper new file
> content).
> 
> By default, diff tries to interpret content history in terms of renames
> and copies when possible, in order to help users. Sometimes this fails -
> while still being correct, it confuses them ;)

Sure, that's one way to look at it, but I disagree. You give the user the way to tell the system the intention of which file moves where, but internally this information is lost and "guessed" incorrectly.

hg seems to do this correctly, the same commands with 'hg diff --git' at the end show:

diff --git a/Makefile b/Makefile
new file mode 100644
diff --git a/a b/b
rename from a
rename to b

 Thomas