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			100 lines
		
	
	
		
			4.4 KiB
		
	
	
	
		
			Plaintext
		
	
The git-cl README describes the git-cl command set.  This document
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describes how code review and git work together in general, intended
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for people familiar with git but unfamiliar with the code review
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process supported by Rietveld.
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== Concepts and terms
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A Rietveld review is for discussion of a single change or patch.  You
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upload a proposed change, the reviewer comments on your change, and
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then you can upload a revised version of your change.  Rietveld stores
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the history of uploaded patches as well as the comments, and can
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compute diffs in between these patches.  The history of a patch is
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very much like a small branch in git, but since Rietveld is
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VCS-agnostic the concepts don't map perfectly.  The identifier for a
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single review+patches+comments in Rietveld is called an "issue".
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Rietveld provides a basic uploader that understands git.  This program
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is used by git-cl, and is included in the git-cl repo as upload.py.
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== Basic interaction with git
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The fundamental problem you encounter when you try to mix git and code
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review is that with git it's nice to commit code locally, while during
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a code review you're often requested to change something about your
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code.  There are a few different ways you can handle this workflow
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with git:
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1) Rewriting a single commit.  Say the origin commit is O, and you
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   commit your initial work in a commit A, making your history like
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   O--A.  After review comments, you commit --amend, effectively
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   erasing A and making a new commit A', so history is now O--A'.
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   (Equivalently, you can use git reset --soft or git rebase -i.)
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2) Writing follow-up commits.  Initial work is again in A, and after
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   review comments, you write a new commit B so your history looks
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   like O--A--B.  When you upload the revised patch, you upload the
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   diff of O..B, not A..B; you always upload the full diff of what
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   you're proposing to change.
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The Rietveld patch uploader just takes arguments to "git diff", so
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either of the above workflows work fine.  If all you want to do is
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upload a patch, you can use the upload.py provided by Rietveld with
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arguments like this:
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  upload.py --server server.com <args to "git diff">
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The first time you upload, it creates a new issue; for follow-ups on
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the same issue, you need to provide the issue number:
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  upload.py --server server.com --issue 1234 <args to "git diff">
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== git-cl to the rescue
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git-cl simplifies the above in the following ways:
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1) "git cl config" puts a persistent --server setting in your .git/config.
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2) The first time you upload an issue, the issue number is associated with
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   the current *branch*.  If you upload again, it will upload on the same
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   issue.  (Note that this association is tied to a branch, not a commit,
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   which means you need a separate branch per review.)
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3) If your branch is "tracking" (in the "git checkout --track" sense)
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   another one (like origin/master), calls to "git cl upload" will
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   diff against that branch by default.  (You can still pass arguments
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   to "git diff" on the command line, if necessary.)
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In the common case, this means that calling simply "git cl upload"
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will always upload the correct diff to the correct place.
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== Patch series
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The above is all you need to know for working on a single patch.
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Things get much more complicated when you have a series of commits
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that you want to get reviewed.  Say your history looks like
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O--A--B--C.  If you want to upload that as a single review, everything
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works just as above.
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But what if you upload each of A, B, and C as separate reviews?
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What if you then need to change A?
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1) One option is rewriting history: write a new commit A', then use
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   git rebase -i to insert that diff in as O--A--A'--B--C as well as
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   squash it.  This is sometimes not possible if B and C have touched
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   some lines affected by A'.
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2) Another option, and the one espoused by software like topgit, is for
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   you to have separate branches for A, B, and C, and after writing A'
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   you merge it into each of those branches.  (topgit automates this
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   merging process.)  This is also what is recommended by git-cl, which
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   likes having different branch identifiers to hang the issue number
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   off of.  Your history ends up looking like:
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       O---A---B---C
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            \   \   \
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             A'--B'--C'
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   Which is ugly, but it accurately tracks the real history of your work, can
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   be thrown away at the end by committing A+A' as a single "squash" commit.
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In practice, this comes up pretty rarely.  Suggestions for better workflows
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are welcome.
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