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Re: How to keep log history when renaming and changing simultaneously




Hi Urs,

On 17/04/2017 13:36, Urs Thuermann wrote:
> Sometimes I need to rename and change a file in one commit.  One
> example would be a file foo.h that begins with
> 
>     #ifndef FOO_H
>     #define FOO_H
> 
> which should be renamed bar.h and have the FOO_H changed to BAR_H.
> In subversion I would
> 
>     svn mv foo.h bar.h; vi bar.h; svn ci
> 
> and then a
> 
>     svn log bar.h
> 
> also shows the history of that file when it was named foo.h.
> 
> This does not work in git.  After committing,
> 
>     git mv foo.h bar.h; vi bar.h; git commit -a
> 
> the command
> 
>     git log --follow bar.h
> 
> shows only the history of the file when it was named bar.h, but not
> its life as foo.h.
> 
> The only workaround I found was to do the rename and the change in two
> separate commits, so that git sees the same name and the same SHA hash
> which allows it to follow the files' history.  This can be a problem
> when the intermediate version with either only the change or only the
> rename doesn't compile correctly.
> 
> Is there a better way to do this in git?
> 
> A similar problem is splitting a file into two files.  With subversion
> I'd do
> 
>     printf "void foo() {}\nint main() { foo(); }\n" > prog.c
>     svn add prog.c; svn ci -m "Add prog.c"
> 
> Then I would split
> 
>     svn cp prog.c foo.c; svn cp prog.c main.c; svn rm prog.c
>     printf "2d\nwq\n" | ed foo.c; printf "1d\nwq\n" | ed main.c
>     svn ci -m "Split prog.c"; svn up
> 
> and I get
> 
>     $ svn log -v
>     ------------------------------------------------------------------------
>     r2 | urs | 2017-04-17 10:03:06 +0200 (Mon, 17 Apr 2017) | 1 line
>     Changed paths:
>        A /foo.c (from /prog.c:1)
>        A /main.c (from /prog.c:1)
>        D /prog.c
>     
>     Split prog.c
>     ------------------------------------------------------------------------
>     r1 | urs | 2017-04-17 10:02:51 +0200 (Mon, 17 Apr 2017) | 1 line
>     Changed paths:
>        A /prog.c
>     
>     Add prog.c
>     ------------------------------------------------------------------------
> 
> And I can also see this when I run svn log on one of both files.	
> How could I do this in git?

For both cases (renaming and splitting), would using `--find-copies` 
work for you? Perhaps with some low threshold value to start with, if 
the default one yields no results.

If interested, adding `--name-status` to the mix will show similarity 
percentage between old and new file(s).


For example, renaming (with edit):

    git log --follow --find-copies=10% --name-status -- bar.h

... yields something like this (sha1/author/date/message omitted 
for brevity):

    commit 2
    ...
    R034    foo.h   bar.h

    commit 1
    ...
    A       foo.h


Another example, splitting (with minor edits):

    git log --find-copies --name-status

... outputs something like this:

    commit 2
    ...
    C090    prog.c  foo.c
    R090    prog.c  main.c

    commit 1
    ...
    A       prog.c


Regards,
Buga