Bug?: 'git log --find-copies' doesn't match 'git log --follow <rev> -- path/to/file'

Bug?: 'git log --find-copies' doesn't match 'git log --follow <rev> -- path/to/file'

[Alexander Pepper]

Hello Again.

I'm not really sure, if this is a bug or if I am missing something, but the following is quite annoying:

$ git version
git version 1.7.6.3
$ git clone https://github.com/voldemort/voldemort.git
$ cd voldemort
$ git log --numstat --find-copies dd4e90f9
...
3       15      contrib/ec2-testing/src/java/voldemort/utils/{StopClusterException.java => ClusterOperation.java}
$ git log --numstat dd4e90f9 -- contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java
...
23      0       contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java
$ git log --numstat --follow dd4e90f9 -- contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java
...
6       10      src/java/voldemort/annotations/concurrency/Immutable.java => contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java

So git log with copy and rename detection on (--find-copies) tells me, that the file StopClusterException.java is copied to ClusterOperation.java. But If I ask git log for that specific file with --follow git claims a copy from Immutable.java to ClusterOperation.java!

I understand, that git doesn't record renames and copies, but only detects it afterwords. But at least I would expect, that git detects the same thing consistently between to (quite) alike flags.

I also tried adding "--find-copies" and "--find-copies-harder" to 'git log --numstat --follow dd4e90f9', but they also result in claiming Immutable.java as the origin of the copy.

Is there a flag to get consistent results between the two or is this really a bug?

Greetings from Berlin
Alex

Re: Bug?: 'git log --find-copies' doesn't match 'git log --follow <rev> -- path/to/file'

[Jeff King]

On Fri, Sep 30, 2011 at 05:32:38PM +0200, Alexander Pepper wrote:

> So git log with copy and rename detection on (--find-copies) tells me,
> that the file StopClusterException.java is copied to
> ClusterOperation.java. But If I ask git log for that specific file
> with --follow git claims a copy from Immutable.java to
> ClusterOperation.java!

I think that --follow uses --find-copies-harder. Did you try:

  git log --numstat --find-copies-harder dd4e90f9

? Does it find Immutable.java as the source?

-Peff

Re: Bug?: 'git log --find-copies' doesn't match 'git log --follow <rev> -- path/to/file'

[Alexander Pepper]

Am 30.09.2011 um 23:38 schrieb Jeff King:

> On Fri, Sep 30, 2011 at 05:32:38PM +0200, Alexander Pepper wrote:
> 
>> So git log with copy and rename detection on (--find-copies) tells me,
>> that the file StopClusterException.java is copied to
>> ClusterOperation.java. But If I ask git log for that specific file
>> with --follow git claims a copy from Immutable.java to
>> ClusterOperation.java!
> 
> I think that --follow uses --find-copies-harder. Did you try:
> 
>  git log --numstat --find-copies-harder dd4e90f9
> 
> ? Does it find Immutable.java as the source?
> 
> -Peff


Using 'git log --numstat --find-copies-harder dd4e90f9' yields "immutable.java" as you expected:

$ git log --numstat --find-copies-harder dd4e90f9
[...]
6       10      src/java/voldemort/annotations/concurrency/Immutable.java => contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java

So is there a way to tell --follow to only use --find-copies instead of --find-copies harder? And what is the advantage of using "--find-copies-harder" over "--find-copies"?

Greetings from Berlin
Alex

-- 
Alexander Pepper
pepper@inf.fu-berlin.de

Re: Bug?: 'git log --find-copies' doesn't match 'git log --follow <rev> -- path/to/file'

[Jeff King]

On Sun, Oct 02, 2011 at 05:10:26PM +0200, Alexander Pepper wrote:

> Using 'git log --numstat --find-copies-harder dd4e90f9' yields "immutable.java" as you expected:
> 
> $ git log --numstat --find-copies-harder dd4e90f9
> [...]
> 6       10      src/java/voldemort/annotations/concurrency/Immutable.java => contrib/ec2-testing/src/java/voldemort/utils/ClusterOperation.java

OK. That at least explains what's going on.

> So is there a way to tell --follow to only use --find-copies instead
> of --find-copies harder?

No, it's hard-coded.

> And what is the advantage of using "--find-copies-harder" over "--find-copies"?

It finds more copies. The rename detection works like this:

  --find-renames: for each newly-created file, consider any deleted
                  files as possible sources

  --find-copies: like above, but also consider any modified files as
                 possible sources

  --find-copies-harder: like above, but consider any file in the
                        repository as a possible source

So in theory --find-copies-harder is the most accurate, but it is also
the most expensive. We can afford to do it for --follow since we're only
considering a small subset of the possible destinations.

So git is saying that your immutable.java is actually a better match;
it's just that we don't usually find it because it wasn't modified in
the same commit. Have you looked at the contents? Is it actually a
better match, or is git wrong?

-Peff