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/usr/share/doc/git/howto

Name	Size	Mode	Actions
coordinate-embargoed-releases.html	29838	0644	edit dl rm
coordinate-embargoed-releases.txt	10823	0644	edit dl rm
keep-canonical-history-correct.html	26249	0644	edit dl rm
keep-canonical-history-correct.txt	6795	0644	edit dl rm
maintain-git.html	41732	0644	edit dl rm
maintain-git.txt	18220	0644	edit dl rm
new-command.html	22001	0644	edit dl rm
new-command.txt	4460	0644	edit dl rm
rebase-from-internal-branch.html	24456	0644	edit dl rm
rebase-from-internal-branch.txt	6310	0644	edit dl rm
rebuild-from-update-hook.html	20387	0644	edit dl rm
rebuild-from-update-hook.txt	3137	0644	edit dl rm
recover-corrupted-blob-object.html	23884	0644	edit dl rm
recover-corrupted-blob-object.txt	5510	0644	edit dl rm
recover-corrupted-object-harder.html	36038	0644	edit dl rm
recover-corrupted-object-harder.txt	14607	0644	edit dl rm
revert-a-faulty-merge.html	30865	0644	edit dl rm
revert-a-faulty-merge.txt	10856	0644	edit dl rm
revert-branch-rebase.html	24740	0644	edit dl rm
revert-branch-rebase.txt	7823	0644	edit dl rm
separating-topic-branches.html	20526	0644	edit dl rm
separating-topic-branches.txt	3356	0644	edit dl rm
setup-git-server-over-http.html	30562	0644	edit dl rm
setup-git-server-over-http.txt	8613	0644	edit dl rm
update-hook-example.html	23272	0644	edit dl rm
update-hook-example.txt	6289	0644	edit dl rm
use-git-daemon.html	19649	0644	edit dl rm
use-git-daemon.txt	2135	0644	edit dl rm
using-merge-subtree.html	20235	0644	edit dl rm
using-merge-subtree.txt	3025	0644	edit dl rm
using-signed-tag-in-pull-request.html	26765	0644	edit dl rm
using-signed-tag-in-pull-request.txt	8282	0644	edit dl rm

Edit: /usr/share/doc/git/howto/separating-topic-branches.txt (3356B)

From: Junio C Hamano <gitster@pobox.com>
Subject: Separating topic branches
Abstract: In this article, JC describes how to separate topic branches.
Content-type: text/asciidoc

How to separate topic branches
==============================

This text was originally a footnote to a discussion about the
behaviour of the git diff commands.

Often I find myself doing that [running diff against something other
than HEAD] while rewriting messy development history.  For example, I
start doing some work without knowing exactly where it leads, and end
up with a history like this:

"master"
        o---o
             \                    "topic"
              o---o---o---o---o---o

At this point, "topic" contains something I know I want, but it
contains two concepts that turned out to be completely independent.
And often, one topic component is larger than the other.  It may
contain more than two topics.

In order to rewrite this mess to be more manageable, I would first do
"diff master..topic", to extract the changes into a single patch, start
picking pieces from it to get logically self-contained units, and
start building on top of "master":

$ git diff master..topic >P.diff
        $ git checkout -b topicA master
        ... pick and apply pieces from P.diff to build
        ... commits on topicA branch.

o---o---o
             /        "topicA"
        o---o"master"
             \                    "topic"
              o---o---o---o---o---o

Before doing each commit on "topicA" HEAD, I run "diff HEAD"
before update-index the affected paths, or "diff --cached HEAD"
after.  Also I would run "diff --cached master" to make sure
that the changes are only the ones related to "topicA".  Usually
I do this for smaller topics first.

After that, I'd do the remainder of the original "topic", but
for that, I do not start from the patchfile I extracted by
comparing "master" and "topic" I used initially.  Still on
"topicA", I extract "diff topic", and use it to rebuild the
other topic:

$ git diff -R topic >P.diff ;# --cached also would work fine
        $ git checkout -b topicB master
        ... pick and apply pieces from P.diff to build
        ... commits on topicB branch.

"topicB"
               o---o---o---o---o
              /
             /o---o---o
            |/        "topicA"
        o---o"master"
             \                    "topic"
              o---o---o---o---o---o

After I am done, I'd try a pretend-merge between "topicA" and
"topicB" in order to make sure I have not missed anything:

$ git pull . topicA ;# merge it into current "topicB"
        $ git diff topic
                                "topicB"
               o---o---o---o---o---* (pretend merge)
              /                   /
             /o---o---o----------'
            |/        "topicA"
        o---o"master"
             \                    "topic"
              o---o---o---o---o---o

The last diff better not to show anything other than cleanups
for cruft.  Then I can finally clean things up:

$ git branch -D topic
        $ git reset --hard HEAD^ ;# nuke pretend merge

"topicB"
               o---o---o---o---o
              /
             /o---o---o
            |/        "topicA"
        o---o"master"

cmd: