Two newbie question: "dead" branches and merging after cherry-pick.

Two newbie question: "dead" branches and merging after cherry-pick.

[Romano Giannetti]

Hi,

   this is a "really-newbie-question"...  git is the first SCM that I try to
   use, and I am really fascinated with it. I develop my software on three
   different PC and git solves all my problems of keeping uptodate with
   myself in a really nice way. 

   I have a couple of doubts that probably are at the very silly level but... 
   Here I go: 

        - I use to work on a topic branch to make test, try solutions for
        bugs, etc. Say I am done with the branch "test-bill-idea". I decide
        it's a dead branch, so that I do not want to see it in day-by-day
        work (git branch, basically), but I do not want to loose it. If I
        delete the branch I will loose all its commit at the next prune,
        correct? There is a way to maintain it as a dead or hidden branch,
        shown for example just by gitk --all? If I tag the tip of the
        branch, and then delete .git/refs/head/test-bill-idea, will the
        "dead branch commits" be preserved by next prune(s)? 

        - Easier: suppose I cheery-picked "abababab" from branch "testing"
        to master branch. What will happen if later I decide to merge
        all "testing" to master branch? I will have a merge conflict (trying
        to apply two times the same fix) or not? 

   Thank you very much for your time! Have a nice week end,

         Romano   

   
-- 
Romano Giannetti             -  Univ. Pontificia Comillas (Madrid, Spain)
Electronic Engineer - phone +34 915 422 800 ext 2416  fax +34 915 596 569
http://www.dea.icai.upcomillas.es/romano/

Re: Two newbie question: "dead" branches and merging after cherry-pick.

[Alex Riesen]

Romano Giannetti, Fri, Jan 27, 2006 18:36:19 +0100:
> - I use to work on a topic branch to make test, try solutions for
> bugs, etc. Say I am done with the branch "test-bill-idea". I decide
> it's a dead branch, so that I do not want to see it in day-by-day
> work (git branch, basically), but I do not want to loose it. If I
> delete the branch I will loose all its commit at the next prune,
> correct? There is a way to maintain it as a dead or hidden branch,
> shown for example just by gitk --all? If I tag the tip of the
> branch, and then delete .git/refs/head/test-bill-idea, will the
> "dead branch commits" be preserved by next prune(s)? 

Yes, it will.

You can actually move the reference file anywhere under .git/refs/,
and "git prune" will never touch it and gitk will show it different
color (looks grey to me). The tags are shown yellow, which can be
associated with "dead for some time" already.

> - Easier: suppose I cheery-picked "abababab" from branch "testing"
> to master branch. What will happen if later I decide to merge
> all "testing" to master branch? I will have a merge conflict (trying
> to apply two times the same fix) or not? 

Yes, you probably will have to deal with a conflict (it can match the
branch to be merged exactly, which is hardly a conflict).

Re: Two newbie question: "dead" branches and merging after cherry-pick.

[Junio C Hamano]

Romano Giannetti <romano@dea.icai.upcomillas.es> writes:

>         - I use to work on a topic branch to make test, try solutions for
>         bugs, etc. Say I am done with the branch "test-bill-idea". I decide
>         it's a dead branch, so that I do not want to see it in day-by-day
>         work (git branch, basically), but I do not want to loose it. ...

First let me make sure if I understand you correctly.

You are done with what you did in the branch for now, but you
have not merged the work to your day-to-day development "master"
for some reason.  In the meantime you would want to switch to
other topic branches to work on other topics, and while working
on them you do not want to "git branch" and "git show-branch" to
show the topic you are done with but not merged yet.  Later you
would want to come back to it to do some interesting stuff with
it (maybe finally merge into "master", or format-patch to send
upstream).  Is that what is happening here?

If so, I would have chosen "postponed" not "dead" to describe
the situation but you said "dead" and that is why I am wondering
if I am getting you correctly.

>         ... If I
>         delete the branch I will loose all its commit at the next prune,
>         correct? ...

Yes.  If you do not have anything under .git/refs pointing at
the tip of a development trail, that trail will be lost by the
next prune.  Even if you do not prune, it would be cumbersome to
find it.  "git lost-found" would find it for you but it still is
cumbersome.

>         ... There is a way to maintain it as a dead or hidden branch,
>         shown for example just by gitk --all? If I tag the tip of the
>         branch, and then delete .git/refs/head/test-bill-idea, will the
>         "dead branch commits" be preserved by next prune(s)? 

Yes.  You have the tag under .git/refs which points at the tip
of that postponed branch head, so the development trail will not
be lost.  When you are done with other topics and would want to
come back to that topic again, you could do this:

	$ git checkout -b test-bill-idea tag-bill-idea-postponed

Until recently I used to have "jc/link" topic branch to play
with "gitlink"-style subproject support suggested by Linus.  It
is not finished yet, and in the meantime I have suggested
another way to do subproject support, which I've been spending
more time on, in "jc/bind" topic branch.  I have not abandoned
"jc/link" topic completely, so I am not ready to do throw away
that branch with "git branch -D jc/link" yet, but at the same
time it clutters output from "git branch".  So I did exactly
what you outlined [*1*]:

	$ git tag hold/jc/gitlink jc/link ;# copy it to tags/
        $ git branch -D jc/link		  ;# delete it from heads/

Now "git branch" would not show it, but "gitk --all" still would.

>         - Easier: suppose I cheery-picked "abababab" from branch "testing"
>         to master branch. What will happen if later I decide to merge
>         all "testing" to master branch? I will have a merge conflict (trying
>         to apply two times the same fix) or not? 

This is easy to experiment so I'd suggest you to try it and tell
us what you see, like this:

	$ git checkout -b test-merge-throwaway master
        $ git cherry-pick abababab
        $ ... play with it, maybe making a couple of commits
        $ git pull . testing

I would not be surprised if this resolves cleanly. If abababab
is the only thing that touches the set of paths it touches,
other than what are in "testing" and what you did since
"testing" forked from "master", it is likely that the merge
would resolve cleanly.

Otherwise you would likely to see conflicts --- in which case
you may want to suggest if/how we can reduce it.  "cherry-pick"
without -r drops a hint of which commit was picked in the commit
log so it _might_ be a good idea to teach git to optionally take
that information into account while doing the merge.  I dunno.

Once you are done experimenting, you can come back to master and
delete the test-merge-throwaway branch:

	$ git checkout master
        $ git branch -D test-merge-throwaway


[Footnote]

*1* As my personal convention, each of my topic branches is
named with two-letter name, '/', and a short topic word, and
postponed tags have names starting with "hold/".  Sticking to a
convention makes it easy for me to do things like this:

	$ git show-branch --topo-order master "heads/??/*"

Re: Two newbie question: "dead" branches and merging after cherry-pick.

[Romano Giannetti]

First of all, 1000 thanks and please forgive me for the broken thread, I was
not subscribed to the list before so I did a copy-and-paste from the web
archive. 

Junio C. Hamano wrote:
> 
> You are done with what you did in the branch for now, but you
> have not merged the work to your day-to-day development "master"
> for some reason.  In the meantime you would want to switch to
> other topic branches to work on other topics, and while working
> on them you do not want to "git branch" and "git show-branch" to
> show the topic you are done with but not merged yet.  Later you
> would want to come back to it to do some interesting stuff with
> it (maybe finally merge into "master", or format-patch to send
> upstream).  Is that what is happening here?
> If so, I would have chosen "postponed" not "dead" to describe
> the situation but you said "dead" and that is why I am wondering
> if I am getting you correctly.

Yes, you have understood perfectly. I called them "dead" because really I do
not think to come back to them ever, but I want to maintain that as "old
story", something of the style "that was an error, store it so that you will
never fall in it again". 
> 
> Yes.  You have the tag under .git/refs which points at the tip
> of that postponed branch head, so the development trail will not
> be lost.  When you are done with other topics and would want to
> come back to that topic again, you could do this:
> 

>     $ git tag hold/jc/gitlink jc/link ;# copy it to tags/
>        $ git branch -D jc/link             ;# delete it from heads/
> 
> Now "git branch" would not show it, but "gitk --all" still would.
>

What I have done (and it seems to work perfectly) is 

    git checkout master
    mkdir .git/refs/olds 
    mv .git/heads/test-bill-idea .git/olds

and it seems to work ok. Thanks! 

    
>         - Easier: suppose I cheery-picked "abababab" from branch "testing"
>         to master branch. What will happen if later I decide to merge
>         all "testing" to master branch? I will have a merge conflict (trying
>         to apply two times the same fix) or not? 
> 
> This is easy to experiment so I'd suggest you to try it and tell
> us what you see, like this:
> 
>   $ git checkout -b test-merge-throwaway master
>        $ git cherry-pick abababab
>        $ ... play with it, maybe making a couple of commits
>        $ git pull . testing
> 
> I would not be surprised if this resolves cleanly. If abababab
> is the only thing that touches the set of paths it touches,
> other than what are in "testing" and what you did since
> "testing" forked from "master", it is likely that the merge
> would resolve cleanly.
> 
> Otherwise you would likely to see conflicts --- in which case
> you may want to suggest if/how we can reduce it.  "cherry-pick"
> without -r drops a hint of which commit was picked in the commit
> log so it _might_ be a good idea to teach git to optionally take
> that information into account while doing the merge.  I dunno.
> 
> Once you are done experimenting, you can come back to master and
> delete the test-merge-throwaway branch:
> 
>       $ git checkout master
>        $ git branch -D test-merge-throwaway
> 

Thanks. I will play a bit with it. I sometime have a bit of fear to not
being able to come back to a good state. I will do my homework and study a
bit more git checkout, branch and reset (this latter gives me a bit of
headheache last time... ;-) ).

Thanks a lot. 
          
-- 
Romano Giannetti             -  Univ. Pontificia Comillas (Madrid, Spain)
Electronic Engineer - phone +34 915 422 800 ext 2416  fax +34 915 596 569
http://www.dea.icai.upcomillas.es/romano/