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$ git log --oneline -5 --author cbeams --before "Fri Mar 26 2009"
e5f4b49 Re-adding ConfigurationPostProcessorTests after its brief removal in r814. @Ignore-ing the testCglibClassesAreLoadedJustInTimeForEnhancement() method as it turns out this was one of the culprits in the recent build breakage. The classloader hacking causes subtle downstream effects, breaking unrelated tests. The test method is still useful, but should only be run on a manual basis to ensure CGLIB is not prematurely classloaded, and should not be run as part of the automated build.
2db0f12 fixed two build-breaking issues: + reverted ClassMetadataReadingVisitor to revision 794 + eliminated ConfigurationPostProcessorTests until further investigation determines why it causes downstream tests to fail (such as the seemingly unrelated ClassPathXmlApplicationContextTests)
147709f Tweaks to package-info.java files
22b25e0 Consolidated Util and MutableAnnotationUtils classes into existing AsmUtils
7f96f57 polishing
$ git log --oneline -5 --author pwebb --before "Sat Aug 30 2014"
5ba3db6 Fix failing CompositePropertySourceTests
84564a0 Rework @PropertySource early parsing logic
e142fd1 Add tests for ImportSelector meta-data
887815f Update docbook dependency and generate epub
ac8326d Polish mockito usage
git log and related tools. There is a vicious cycle here: because the commit history is unstructured and inconsistent, one doesn’t spend much time using or taking care of it. And because it doesn’t get used or taken care of, it remains unstructured and inconsistent.
But a well-cared for log is a beautiful and useful thing. git blame, revert, rebase, log, shortlog and other subcommands come to life. Reviewing others’ commits and pull requests becomes something worth doing, and suddenly can be done independently. Understanding why something happened months or years ago becomes not only possible but efficient.
A project’s long-term success rests (among other things) on its maintainability, and a maintainer has few tools more powerful than his project’s log. It’s worth taking the time to learn how to care for one properly. What may be a hassle at first soon becomes habit, and eventually a source of pride and productivity for all involved.
In this post, I am addressing just the most basic element of keeping a healthy commit history: how to write an individual commit message. There are other important practices like commit squashing that I am not addressing here. Perhaps I’ll do that in a subsequent post.
Most programming languages have well-established conventions as to what constitutes idiomatic style, i.e. naming, formatting and so on. There are variations on these conventions, of course, but most developers agree that picking one and sticking to it is far better than the chaos that ensues when everybody does their own thing.
A team’s approach to its commit log should be no different. In order to create a useful revision history, teams should first agree on a commit message convention that defines at least the following three things:
Style. Markup syntax, wrap margins, grammar, capitalization, punctuation. Spell these things out, remove the guesswork, and make it all as simple as possible. The end result will be a remarkably consistent log that’s not only a pleasure to read but that actually does get read on a regular basis.
Content. What kind of information should the body of the commit message (if any) contain? What should it not contain?
Metadata. How should issue tracking IDs, pull request numbers, etc. be referenced?
Fortunately, there are well-established conventions as to what makes an idiomatic Git commit message. Indeed, many of them are assumed in the way certain Git commands function. There’s nothing you need to re-invent. Just follow the seven rules below and you’re on your way to committing like a pro.
Summarize changes in around 50 characters or less
More detailed explanatory text, if necessary. Wrap it to about 72
characters or so. In some contexts, the first line is treated as the
subject of the commit and the rest of the text as the body. The
blank line separating the summary from the body is critical (unless
you omit the body entirely); various tools like `log`, `shortlog`
and `rebase` can get confused if you run the two together.
Explain the problem that this commit is solving. Focus on why you
are making this change as opposed to how (the code explains that).
Are there side effects or other unintuitive consequences of this
change? Here's the place to explain them.
Further paragraphs come after blank lines.
- Bullet points are okay, too
- Typically a hyphen or asterisk is used for the bullet, preceded
by a single space, with blank lines in between, but conventions
vary here
If you use an issue tracker, put references to them at the bottom,
like this:
Resolves: #123
See also: #456, #789
git commit manpage:
Though not required, it’s a good idea to begin the commit message with a single short (less than 50 character) line summarizing the change, followed by a blank line and then a more thorough description. The text up to the first blank line in a commit message is treated as the commit title, and that title is used throughout Git. For example, Git-format-patch(1) turns a commit into email, and it uses the title on the Subject line and the rest of the commit in the body.
Firstly, not every commit requires both a subject and a body. Sometimes a single line is fine, especially when the change is so simple that no further context is necessary. For example:
Fix typo in introduction to user guide
git showorgit difforgit log -p.
If you’re committing something like this at the command line, it’s easy to use the -m option to git commit:
$ git commit -m"Fix typo in introduction to user guide"
Derezz the master control program
MCP turned out to be evil and had become intent on world domination.
This commit throws Tron's disc into MCP (causing its deresolution)
and turns it back into a chess game.
-m option. You’re better off writing the message in a proper text editor. If you do not already have an editor set up for use with Git at the command line, read this section of Pro Git.
In any case, the separation of subject from body pays off when browsing the log. Here’s the full log entry:
$ git log
commit 42e769bdf4894310333942ffc5a15151222a87be
Author: Kevin Flynn <kevin@flynnsarcade.com>
Date: Fri Jan 01 00:00:00 1982 -0200
Derezz the master control program
MCP turned out to be evil and had become intent on world domination.
This commit throws Tron's disc into MCP (causing its deresolution)
and turns it back into a chess game.
git log --oneline, which prints out just the subject line:
$ git log --oneline
42e769 Derezz the master control program
git shortlog, which groups commits by user, again showing just the subject line for concision:
$ git shortlog
Kevin Flynn (1):
Derezz the master control program
Alan Bradley (1):
Introduce security program "Tron"
Ed Dillinger (3):
Rename chess program to "MCP"
Modify chess program
Upgrade chess program
Walter Gibbs (1):
Introduce protoype chess program
And will truncate any subject line longer than 72 characters with an ellipsis:
So shoot for 50 characters, but consider 72 the hard limit.
git merge reads:
Merge branch 'myfeature'
git revert:
Revert "Add the thing with the stuff"
This reverts commit cc87791524aedd593cff5a74532befe7ab69ce9d.
Merge pull request #123 from someuser/somebranch
commit eb0b56b19017ab5c16c745e6da39c53126924ed6
Author: Pieter Wuille <pieter.wuille@gmail.com>
Date: Fri Aug 1 22:57:55 2014 +0200
Simplify serialize.h's exception handling
Remove the 'state' and 'exceptmask' from serialize.h's stream
implementations, as well as related methods.
As exceptmask always included 'failbit', and setstate was always
called with bits = failbit, all it did was immediately raise an
exception. Get rid of those variables, and replace the setstate
with direct exception throwing (which also removes some dead
code).
As a result, good() is never reached after a failure (there are
only 2 calls, one of which is in tests), and can just be replaced
by !eof().
fail(), clear(n) and exceptions() are just never called. Delete
them.
git rm when you delete a file, and doing the right stuff with git when you rename one. Where everything falls apart is when you start trying to commit, merge, rebase, or do sophisticated history analysis through the IDE.
When it comes to wielding the full power of Git, it’s command-line all the way.
Remember that whether you use Bash or Zsh or Powershell, there are tab completion scripts that take much of the pain out of remembering the subcommands and switches.