Re: retrospective move

[Thomas Rast <trast@student.ethz.ch>]

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Santi Béjar wrote:
> 2009/2/4 Thomas Rast <trast@student.ethz.ch>:
> > jemmyw wrote:
> >>
> >> Hi. Awhile ago I copied some files in my local repo then commited. In another
> >> commit I deleted the original files, so essentially I did a mv that git
> >> doesn't know about. Now I'm trying to merge from another branch where
> >> changes have happened to the files in their original locations, and it's
> >> making the merge somewhat difficult. Is there a way to ease this?
> >
> > Git never "knows" about a move, it only detects them after the fact.
> > A corollary of this is that 'git mv a b' is more or less the same as
> > 'cp a b; git rm a; git add b'.
> >
> > Now since you have a copy followed by a removal in two separate
> > commits, the merge logic won't treat this as a rename.
> 
> I don't think it holds. Git only sees the endpoints and the bases, it
> does not matter if the "move" was actually two commits. Maybe they
> have changed dramatically and git is not able to detect the rename (or
> the files are small). Another possible cause could be that you have a
> lot of renames (see config merge.renamelimit).

Hmm, you're right.  I stand corrected.

Here's a sequence of commands that makes a test case:

  git init
  seq 1 10 > A
  git add A
  git commit -m initial
  seq 11 15 >> A
  git commit -m second A
  seq 16 20 >> A
  git commit -m third
  git checkout -b side HEAD~2
  cp A B
  git add B
  git commit -m copy
  seq 3 10 > B               # <--
  git commit -m edit B
  git rm A
  git commit -m delete

Then running

  git merge master

goes through cleanly, but changing the line indicated above to 'seq 5
10' makes it less similar, falling through the detection and causing a
conflict.  The minimum required similarity for merges does not seem to
be configurable unfortunately.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch

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