Retry conflicting merge with matching line endings?

Retry conflicting merge with matching line endings?

[skillzero]

I've been running into a lot of merge conflicts due to line endings
changing. For example, I branch from master when a file has CRLF line
endings (incorrectly) then somebody fixes a bug in that file (still
has CRLF line endings) on master then I realize the file should have
LF line endings so I change them. When I try to rebase on master
later, I get a merge conflict because it looks like every line has
changed and it conflicts with that other bug fix.

Would it be reasonable that if you get a conflict during a merge and
the line endings of the two commits are different then change the line
endings to match, retry the merge of that file, then apply the line
ending change commit?

Re: Retry conflicting merge with matching line endings?

[Junio C Hamano]

skillzero@gmail.com writes:

> I've been running into a lot of merge conflicts due to line endings
> changing. For example, I branch from master when a file has CRLF line
> endings (incorrectly) then somebody fixes a bug in that file (still
> has CRLF line endings) on master then I realize the file should have
> LF line endings so I change them. When I try to rebase on master
> later, I get a merge conflict because it looks like every line has
> changed and it conflicts with that other bug fix.
>
> Would it be reasonable that if you get a conflict during a merge and
> the line endings of the two commits are different then change the line
> endings to match, retry the merge of that file, then apply the line
> ending change commit?

This is not specific to fixing line ending but applies any "global token
replacement" (e.g. you renamed a variable) operation in general.

Suppose the conflicted path is hello.c when you were merging branch
"other", e.g. 

	$ git merge other
	$ git ls-files -u
        100644 b040a96e50... 1	hello.c	
	100644 6b9c715d21... 2	hello.c
	100644 1c57d4c958... 3	hello.c

You can first extract the blobs involved into plain files, apply such
"global token replacement" (be it fixing the line ending or renaming a
variable) to the common ancestor version and the other's version, and run
three-way file-level merge.

	$ git cat-file blob :1:hello.c | replacement_filter >ancestor
        $ git cat-file blob :2:hello.c >mine
        $ git cat-file blob :3:hello.c | replacement_filter >theirs
	$ git merge-file mine ancestor theirs

where replacement_filter would be whatever global replacement you did to
your version since the ancestor (e.g. dos2unix).

The "mine" file merge-file leaves will hopefully have much smaller
conflicts, as it won't have to see your line endings change.  If it looks
Ok, cat it into hello.c and "git add" it.

Re: Retry conflicting merge with matching line endings?

[skillzero]

On Tue, Feb 17, 2009 at 6:18 PM, Junio C Hamano <gitster@pobox.com> wrote:
>
> This is not specific to fixing line ending but applies any "global token
> replacement" (e.g. you renamed a variable) operation in general.

Thanks for the details. I was previously resolving things in a more
tedious manner and your steps will make things easier for me.

What I was curious about though is whether it would be reasonable for
me to submit a patch to have git automatically try this for the
special case of line endings (possibly implemented as a general token
replacement scheme with built-in filters for line endings)?