threads / bug / 35053

Bug? Files are losing history after subtree merge

Subject: Bug? Files are losing history after subtree merge

## tl;dr

5 messages between Oct 2, 2013 and Oct 2, 2013.

replies: 4people: 2as markdown or json

Ralf Thielow· Oct 2, 2013, 19:20 UTC · lore

Hi,

recently I did a merge where a complete repo shall be merged into a specific directory of another repo. I tried both the "subtree" merge strategy and the option "-Xsubtree=<dir>" of "recursive". I noticed that in both cases somehow the history of single files were lost during these merges (with history I mean 'git log <file>' and 'git log --follow <file>'). I've worked around this by merging without 'subtree' and moving the dirs/files manually. In this case the file history was there.

I've added a test case below for that behaviour. It doesn't catch "-S recursive -Xsubtree=<dir>" but it should show the issue (hopefully:).

Ralf
---
 t/t6029-merge-subtree.sh | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/t/t6029-merge-subtree.sh b/t/t6029-merge-subtree.sh
index 73fc240..e9a97d7 100755
--- a/t/t6029-merge-subtree.sh
+++ b/t/t6029-merge-subtree.sh
@@ -61,6 +61,14 @@ test_expect_success 'initial merge' '
 	test_cmp expected actual
 '
 
+test_expect_failure 'file keeps history after subtree merge' '
+	cd ../git-gui &&
+	git log --follow git-gui.sh >../git/expected &&
+	cd ../git &&
+	git log --follow git-gui/git-gui.sh >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'merge update' '
 	cd ../git-gui &&
 	echo git-gui2 > git-gui.sh &&

-- 
1.8.4.652.g0d6e0ce

Matthieu Moy· Oct 2, 2013, 19:42 UTC · re: Ralf Thielow · lore

Re: Bug? Files are losing history after subtree merge

Ralf Thielow <ralf.thielow@gmail.com> writes:

Show 9 quoted lines

> Hi,
>
> recently I did a merge where a complete repo shall be
> merged into a specific directory of another repo. I
> tried both the "subtree" merge strategy and the option
> "-Xsubtree=<dir>" of "recursive". I noticed that in both
> cases somehow the history of single files were lost
> during these merges (with history I mean 'git log <file>'
> and 'git log --follow <file>').

This is a known bug of "git log --follow": it does not follow accross subtree merge. But your history is still there (try gitk on your project for example).

Technically, a subtree merge is a merge commit in which files are renamed compared to the second parent. --follow does not manage this case.

Show 16 quoted lines

> diff --git a/t/t6029-merge-subtree.sh b/t/t6029-merge-subtree.sh
> index 73fc240..e9a97d7 100755
> --- a/t/t6029-merge-subtree.sh
> +++ b/t/t6029-merge-subtree.sh
> @@ -61,6 +61,14 @@ test_expect_success 'initial merge' '
>  	test_cmp expected actual
>  '
>  
> +test_expect_failure 'file keeps history after subtree merge' '
> +	cd ../git-gui &&
> +	git log --follow git-gui.sh >../git/expected &&
> +	cd ../git &&
> +	git log --follow git-gui/git-gui.sh >actual &&
> +	test_cmp expected actual
> +'
> +

That would actually be good to add a failing test to "document" the failure.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Ralf Thielow· Oct 2, 2013, 20:10 UTC · re: Matthieu Moy · lore

Re: Bug? Files are losing history after subtree merge

On Wed, Oct 2, 2013 at 9:42 PM, Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> wrote:

Show 20 quoted lines

> Ralf Thielow <ralf.thielow@gmail.com> writes:
>
>> Hi,
>>
>> recently I did a merge where a complete repo shall be
>> merged into a specific directory of another repo. I
>> tried both the "subtree" merge strategy and the option
>> "-Xsubtree=<dir>" of "recursive". I noticed that in both
>> cases somehow the history of single files were lost
>> during these merges (with history I mean 'git log <file>'
>> and 'git log --follow <file>').
>
> This is a known bug of "git log --follow": it does not follow accross
> subtree merge. But your history is still there (try gitk on your project
> for example).
>
> Technically, a subtree merge is a merge commit in which files are
> renamed compared to the second parent. --follow does not manage this
> case.
>

Thanks for explanation. I knew the history of the repo is there, but the history of single files (and the ability to look at it) is so important that subtree-merges aren't an option for us. Such merges are rarely, luckily, but it would be nice to get it work.

Thanks

Show 23 quoted lines

>> diff --git a/t/t6029-merge-subtree.sh b/t/t6029-merge-subtree.sh
>> index 73fc240..e9a97d7 100755
>> --- a/t/t6029-merge-subtree.sh
>> +++ b/t/t6029-merge-subtree.sh
>> @@ -61,6 +61,14 @@ test_expect_success 'initial merge' '
>>       test_cmp expected actual
>>  '
>>
>> +test_expect_failure 'file keeps history after subtree merge' '
>> +     cd ../git-gui &&
>> +     git log --follow git-gui.sh >../git/expected &&
>> +     cd ../git &&
>> +     git log --follow git-gui/git-gui.sh >actual &&
>> +     test_cmp expected actual
>> +'
>> +
>
> That would actually be good to add a failing test to "document" the
> failure.
>
> --
> Matthieu Moy
> http://www-verimag.imag.fr/~moy/

Matthieu Moy· Oct 2, 2013, 20:21 UTC · lore

Re: Bug? Files are losing history after subtree merge

Ralf Thielow <ralf.thielow@gmail.com> writes:

> Thanks for explanation.
> I knew the history of the repo is there, but the history of single files
> (and the ability to look at it)

There is no such thing as "single file history" in Git. Git knows about the history of the project, and knows which files were there at each commit. Then, some commands can walk through history following the history of a file. "git blame" is very good at it, and should work with subtree merges. "git log --follow" is a quick hack that nobody bothered to fix up to now (sadly).

You can use workarounds like

  git log -- '*git-gui.sh'

(from the toplevel), to view each commit that touched a file whose name ends with git-gui.sh. It won't follow actual renames, and may show false positive if you have several files with the same basename. But it may help.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Ralf Thielow· Oct 2, 2013, 20:44 UTC · re: Matthieu Moy · lore

Re: Bug? Files are losing history after subtree merge

On Wed, Oct 2, 2013 at 10:21 PM, Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> wrote:

Show 13 quoted lines

> Ralf Thielow <ralf.thielow@gmail.com> writes:
>
>> Thanks for explanation.
>> I knew the history of the repo is there, but the history of single files
>> (and the ability to look at it)
>
> There is no such thing as "single file history" in Git. Git knows about
> the history of the project, and knows which files were there at each
> commit. Then, some commands can walk through history following the
> history of a file. "git blame" is very good at it, and should work with
> subtree merges. "git log --follow" is a quick hack that nobody bothered
> to fix up to now (sadly).
>

Yeah From a user perspective there is a "single file history", isn't it? And in this case the history is gone. At least in the subtree case...

> You can use workarounds like
>
>   git log -- '*git-gui.sh'
>

"My" users are using gui tools, so there's sadly no chance to change the commands. I just wanted to mention the issue but I've worked around it so it's no problem anymore.

Show 8 quoted lines

> (from the toplevel), to view each commit that touched a file whose name
> ends with git-gui.sh. It won't follow actual renames, and may show false
> positive if you have several files with the same basename. But it may
> help.
>
> --
> Matthieu Moy
> http://www-verimag.imag.fr/~moy/