threads / discuss / 15853

git confused by rename

Subject: git confused by rename

## tl;dr

6 messages between Oct 10, 2008 and Oct 10, 2008.

replies: 5people: 3as markdown or json

Michael P. Soulier· Oct 10, 2008, 14:41 UTC · lore

# On branch ajax-callrecording # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # modified: js/urls.py # modified: js/views.py # modified: scrc/urls.py # modified: scrc/views.py # new file: templates/js/scrc.js # modified: templates/js/teleworker.js # renamed: templates/scrc/index.html -> templates/scrc/cres_taps.html # modified: templates/scrc/index.html

Looking at the last two lines here, there is obviously an issue.

I created a new cres_taps.html file, and modified the index.html file, and for some reason Git thinks that I renamed index.html.

Looks like a bug, unless I'm missing something.
Mike
-- 
Michael P. Soulier <msoulier@digitaltorque.ca>
"Any intelligent fool can make things bigger and more complex... It takes a
touch of genius - and a lot of courage to move in the opposite direction."
--Albert Einstein
Junio C Hamano· Oct 10, 2008, 15:44 UTC · re: Michael P. Soulier · lore

Re: git confused by rename

"Michael P. Soulier" <msoulier@digitaltorque.ca> writes:
> #       renamed:    templates/scrc/index.html -> templates/scrc/cres_taps.html
> #       modified:   templates/scrc/index.html
>
> Looking at the last two lines here, there is obviously an issue.
I am puzzled.

Looking at wt-status.c "renamed: A -> B" will be shown only when A and B are similar enough *and* there is no A remaining in the final result, and in such a case, "modified: A" should not be shown. Because git does not care how you created B (IOW, it does not matter if B was typed from scratch with copying and pasting, or created by copying and editing), the "renamed: A -> B" entry itself is not surprising nor look like a bug at all, but its presense at the same time as "modified: A" does feel very fishy.

Junio C Hamano· Oct 10, 2008, 15:54 UTC · re: Junio C Hamano · lore

Re: git confused by rename

Junio C Hamano <gitster@pobox.com> writes:
Show 8 quoted lines
> "Michael P. Soulier" <msoulier@digitaltorque.ca> writes:
>
>> #       renamed:    templates/scrc/index.html -> templates/scrc/cres_taps.html
>> #       modified:   templates/scrc/index.html
>>
>> Looking at the last two lines here, there is obviously an issue.
>
> I am puzzled.
Not anymore.
> Looking at wt-status.c "renamed: A -> B" will be shown only when A and B
> are similar enough *and* there is no A remaining in the final result, and
> in such a case, "modified: A" should not be shown.
Except for one case.
Show 5 quoted lines
> Because git does not
> care how you created B (IOW, it does not matter if B was typed from
> scratch with copying and pasting, or created by copying and editing), the
> "renamed: A -> B" entry itself is not surprising nor look like a bug at
> all,...

The above observation of mine is correct, but I forgot that "git status" (and the comment in the commit template from "git commit") is generated internally with "diff-index -B -M". So if

 (0) had A but not B in the HEAD commit;
 (1) you created B that is very similar to the original A; and
 (2) you modified A beyond recognition;
then git will say "A was modified and B was created by renaming A".
> ... but its presense at the same time as "modified: A" does feel very
> fishy.
So this is not fishy anymore.

This however makes me wonder if "diff-index -B -M" should say B is copied (instead of being renamed) from A and A is modified in such a case. I do not think we would want to make such a change without thinking things, through.

Björn Steinbrink· Oct 10, 2008, 16:19 UTC · re: Junio C Hamano · lore

Re: git confused by rename

On 2008.10.10 08:54:50 -0700, Junio C Hamano wrote:
Show 25 quoted lines
> Junio C Hamano <gitster@pobox.com> writes:
> > Because git does not care how you created B (IOW, it does not matter
> > if B was typed from scratch with copying and pasting, or created by
> > copying and editing), the "renamed: A -> B" entry itself is not
> > surprising nor look like a bug at all,...
> 
> The above observation of mine is correct, but I forgot that "git status"
> (and the comment in the commit template from "git commit") is generated
> internally with "diff-index -B -M".  So if
> 
>  (0) had A but not B in the HEAD commit;
>  (1) you created B that is very similar to the original A; and
>  (2) you modified A beyond recognition;
> 
> then git will say "A was modified and B was created by renaming A".
> 
> > ... but its presense at the same time as "modified: A" does feel very
> > fishy.
> 
> So this is not fishy anymore.
> 
> This however makes me wonder if "diff-index -B -M" should say B is copied
> (instead of being renamed) from A and A is modified in such a case.  I do
> not think we would want to make such a change without thinking things,
> through.

Oh, heh, my patch doesn't help in that case. It's still modify + rename with it, of course, as -B still breaks the stuff apart. Me being confused about -M reporting copies in some cases remains though, I had really expected that only -C would detect copies. Of course, this confusion is purely from a user's point of view, I have zero knowledge about the involved code...

Björn
Michael P. Soulier· Oct 10, 2008, 22:08 UTC · re: Junio C Hamano · lore

Re: git confused by rename

On 10/10/08 Junio C Hamano said:
Show 7 quoted lines
> The above observation of mine is correct, but I forgot that "git status"
> (and the comment in the commit template from "git commit") is generated
> internally with "diff-index -B -M".  So if
> 
>  (0) had A but not B in the HEAD commit;
>  (1) you created B that is very similar to the original A; and
>  (2) you modified A beyond recognition;
Which, FTR, is what I did. 

I copied A -> B for its boilerplate, and then hacked them both up, although B consisted mostly of content that I removed from A (a refactoring exercise).

> This however makes me wonder if "diff-index -B -M" should say B is copied
> (instead of being renamed) from A and A is modified in such a case.  I do
> not think we would want to make such a change without thinking things,
> through.

Gotcha. Indeed though, I did cp A -> B, and if A still exists then it obviously was not renamed.

Thanks, Mike

-- 
Michael P. Soulier <msoulier@digitaltorque.ca>
"Any intelligent fool can make things bigger and more complex... It
takes a touch of genius - and a lot of courage to move in the opposite
direction." --Albert Einstein
Björn Steinbrink· Oct 10, 2008, 16:08 UTC · re: Junio C Hamano · lore

[PATCH] git-status: Detect copies as well as renames

Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de>
---
On 2008.10.10 08:44:08 -0700, Junio C Hamano wrote:
Show 17 quoted lines
> "Michael P. Soulier" <msoulier@digitaltorque.ca> writes:
> 
> > #       renamed:    templates/scrc/index.html -> templates/scrc/cres_taps.html
> > #       modified:   templates/scrc/index.html
> >
> > Looking at the last two lines here, there is obviously an issue.
> 
> I am puzzled.
> 
> Looking at wt-status.c "renamed: A -> B" will be shown only when A and
> B are similar enough *and* there is no A remaining in the final
> result, and in such a case, "modified: A" should not be shown.
> Because git does not care how you created B (IOW, it does not matter
> if B was typed from scratch with copying and pasting, or created by
> copying and editing), the "renamed: A -> B" entry itself is not
> surprising nor look like a bug at all, but its presense at the same
> time as "modified: A" does feel very fishy.

Maybe something like this is required? The "1" meant that only renames were to be detected, so I'm quite puzzled why it detects copies in some cases at all. At least some trivial:

cp Makefile Makefile2 echo 123 >> Makefile git add Makefile*

Now correctly shows the Makefile2 being a copy of Makefile, while the old behaviour was to simply show it as a new file. _BUT_ when you also did:

git mv Makefile Makefile3

You see a rename of Makefile and a copy of Makefile. Even though we didn't request copy detection... Hu?

I feel like stabbing in the dark though, so I intentionally left out a description in the commit message that tells why this change is good. I simply have no idea, it just _felt_ better. ;-)

Björn
 wt-status.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/wt-status.c b/wt-status.c
index 889e50f..3d645b9 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -210,7 +210,7 @@ static void wt_status_print_updated(struct wt_status *s)
 	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = wt_status_print_updated_cb;
 	rev.diffopt.format_callback_data = s;
-	rev.diffopt.detect_rename = 1;
+	rev.diffopt.detect_rename = DIFF_DETECT_COPY;
 	rev.diffopt.rename_limit = 200;
 	rev.diffopt.break_opt = 0;
 	run_diff_index(&rev, 1);
@@ -310,7 +310,7 @@ static void wt_status_print_verbose(struct wt_status *s)
 	init_revisions(&rev, NULL);
 	setup_revisions(0, NULL, &rev, s->reference);
 	rev.diffopt.output_format |= DIFF_FORMAT_PATCH;
-	rev.diffopt.detect_rename = 1;
+	rev.diffopt.detect_rename = DIFF_DETECT_COPY;
 	rev.diffopt.file = s->fp;
 	rev.diffopt.close_file = 0;
 	run_diff_index(&rev, 1);
-- 
1.6.0.2.307.gc427.dirty

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