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Summary: See task and P91, this just adapts my Discussion post to be more general. I'll follow up by linking to it from the Arcanist error message. Test Plan: Read the document. Reviewed By: jungejason Reviewers: jungejason, tuomaspelkonen, aran CC: aran, jungejason Differential Revision: 701
54 lines
3 KiB
Text
54 lines
3 KiB
Text
@title Differential User Guide: Large Changes
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@group userguide
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Dealing with huge changesets, and when **not** to use Differential.
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= Overview =
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When you want code review for a given changeset, Differential is not always the
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right tool to use. The rule of thumb is that you should only send changes to
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Differential if you expect humans to review the actual differences in the source
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code from the web interface. This should cover the vast majority of changes but,
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for example, you usually should //not// submit changes like these through
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Differential:
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- Committing an entire open source project to a private repo somewhere so
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you can fork it or link against it.
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- Committing an enormous text datafile, like a list of every English word or a
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dump of a database.
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- Making a trivial (e.g., find/replace) edit to 10,000 files.
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You can still try submitting these kinds of changes, but you may encounter
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problems getting them to work (database or connection timeouts, for example).
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Differential is pretty fast and scalable, but at some point either it or the
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browser will break down: you simply can't show nine million files on a webpage.
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More importantly, in all these cases, the text of the changes won't be reviewed
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by a human. The metadata associated with the change is what needs review (e.g.,
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what are you checking in, where are you putting it, and why? Does the change
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make sense? In the case of automated transformations, what script did you use?).
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To get review for these types of changes, one of these strategies will usually
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work better than trying to get the entire change into Differential:
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- Send an email/AIM/IRC to your reviewer(s) like "Hey, I'm going to check in
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the source for MySQL 9.3.1 to /full/path/to/whatever. The change is staged
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in /home/whatever/path/somewhere if you want to take a look. Can I put your
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name on the review?". This is best for straightforward changes. The reviewer
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is not going to review MySQL's source itself, instead they are reviewing the
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change metadata: which version are you checking in, why are you checking it
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in, and where are you putting it?
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- Create a Differential revision with only the metadata, like the script you
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used to make automated changes or a text file explaining what you're doing,
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and maybe a sample of some of the changes if they were automated. Include a
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link to where the changes are staged so reviewers can look at the actual
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changeset if they want to. This is best for more complicated changes, since
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Differential can still be used for discussion and provide a permanent record
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others can refer to.
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In both cases, you won't be able to use "arc commit" or "arc amend" to actually
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push the change. Just use "svn" or "git" and manually edit the commit message
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instead. (It is normally sufficient to add a "Reviewed By: <username>" field.)
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These kinds of changes are generally rare and don't have much in common, which
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is why there's no explicit support for them in Differential. If you frequently
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run into cases which Differential doesn't handle, let us know what they are.
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