f4609b896f
This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because there is some breakage in the git build related to the netrc credentials helper which someone has taken care of in nixpkgs. The stable channel is not used for anything other than git, so this should be fine. Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb
94 lines
3.3 KiB
Text
94 lines
3.3 KiB
Text
From: Junio C Hamano <gitster@pobox.com>
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Subject: Separating topic branches
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Abstract: In this article, JC describes how to separate topic branches.
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Content-type: text/asciidoc
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How to separate topic branches
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==============================
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This text was originally a footnote to a discussion about the
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behaviour of the git diff commands.
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Often I find myself doing that [running diff against something other
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than HEAD] while rewriting messy development history. For example, I
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start doing some work without knowing exactly where it leads, and end
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up with a history like this:
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"master"
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o---o
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\ "topic"
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o---o---o---o---o---o
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At this point, "topic" contains something I know I want, but it
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contains two concepts that turned out to be completely independent.
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And often, one topic component is larger than the other. It may
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contain more than two topics.
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In order to rewrite this mess to be more manageable, I would first do
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"diff master..topic", to extract the changes into a single patch, start
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picking pieces from it to get logically self-contained units, and
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start building on top of "master":
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$ git diff master..topic >P.diff
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$ git checkout -b topicA master
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... pick and apply pieces from P.diff to build
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... commits on topicA branch.
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o---o---o
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/ "topicA"
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o---o"master"
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\ "topic"
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o---o---o---o---o---o
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Before doing each commit on "topicA" HEAD, I run "diff HEAD"
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before update-index the affected paths, or "diff --cached HEAD"
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after. Also I would run "diff --cached master" to make sure
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that the changes are only the ones related to "topicA". Usually
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I do this for smaller topics first.
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After that, I'd do the remainder of the original "topic", but
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for that, I do not start from the patchfile I extracted by
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comparing "master" and "topic" I used initially. Still on
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"topicA", I extract "diff topic", and use it to rebuild the
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other topic:
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$ git diff -R topic >P.diff ;# --cached also would work fine
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$ git checkout -b topicB master
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... pick and apply pieces from P.diff to build
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... commits on topicB branch.
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"topicB"
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o---o---o---o---o
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/
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/o---o---o
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|/ "topicA"
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o---o"master"
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\ "topic"
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o---o---o---o---o---o
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After I am done, I'd try a pretend-merge between "topicA" and
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"topicB" in order to make sure I have not missed anything:
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$ git pull . topicA ;# merge it into current "topicB"
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$ git diff topic
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"topicB"
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o---o---o---o---o---* (pretend merge)
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/ /
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/o---o---o----------'
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|/ "topicA"
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o---o"master"
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\ "topic"
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o---o---o---o---o---o
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The last diff better not to show anything other than cleanups
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for cruft. Then I can finally clean things up:
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$ git branch -D topic
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$ git reset --hard HEAD^ ;# nuke pretend merge
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"topicB"
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o---o---o---o---o
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/
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/o---o---o
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|/ "topicA"
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o---o"master"
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