Re: merge removed content back into current content

"Elijah Newren" [off-list ref] wrote in message 

quoted

news:AANLkTimxHbCktv=kaq0UfV+u1kH1Pb2LYA2Xi=qkgduW@mail.gmail.com...

On Fri, Sep 24, 2010 at 9:06 PM, Neal Kreitzinger [off-list ref] wrote:

quoted

How do I tell git to merge a single program from an old commit into the
current version of that program in the HEAD commit? In this scenario, I
want to get back some removed code but still keep the new code.

e.g.

Commit-1 = initial commit containing Program-A, and other programs

Commit-2 = add Changeset-1 to Program-A , and make changes to other 
programs

Commit-3 = remove Changeset-1 from Program-A, then add Changeset-2 to
Program-A, and make changes to other programs

*desired* Commit-4 = only merge Program-A from Commit-2 into Program-A of
Commit-3, and don't change any other programs
(in other words, get my old changes from Commit-2 back, but don't loose 
the
new changes from Commit-3)

Does something like:
 git diff commit1 commit2 -- ProgramA | git apply
do what you need?

All of our source conflicts because we add a user/datestamp to the first 
line.  We do this to insure the programmer reviews the merge.
However, I never used git apply before so that was interesting to learn.

If diff+apply doesn't work[1], you can try
 git cat-file -p commit1:ProgramA > base
 git cat-file -p commit2:ProgramA > other
 git cat-file -p commit3:ProgramA > current
 git merge-file current base other

This method is also something new to me, but it seems too manual.  It also 
does not do the normal git merge where the results are in the index.  An 
easier method is to do this:
git difftool commit1 commit2 -- ProgramA
and then use kdiff3's merge option.  this does not include the common 
ancestor as a reference like a normal git merge conflict followed by git 
mergetool (kdiff3), but is user friendly.  However, I'm not crazy about it 
because I'd rather have the merge results in the index and use git mergetool 
like I do for commit merges.

[1] e.g. would cause conflicts -- btw, does anyone know how to force
git apply to proceed and add conflict markers if necessary rather than
just bailing out?