Using git to explore the history of a file change...

[al-the-x]

The invoke() function in src/auto/injector.js jumps through some hoops to allow two different method signatures: one with locals and one without. Using some of the following techniques, figure out:

1. When that change occurred
2. What was the previous function signature
3. Why did it change?

The git log subcommand will be your friend here. Github has a built-in version -- the "history" panel -- that you can fall back on. Explore the various options to git log and pay special attention to the flags -S, -G, --pickaxe-regex and --word-diff. They'll help.

[pomerantsev]

Unfortunately, I've had a hard time figuring out what these lines are meant to do.
They were introduced in commit 4b1695ec61a with strict-di mode. The fourth parameter to invoke (serviceName) is used to provide meaningful error messages.
But never in the source code invoke() is called with a string as a third parameter. The fourth parameter is also not documented, so when called from outside of the framework's source, the third parameter is meant to be the locals object.
I've also tried running the unit tests with the first four lines of invoke commented out. It yields no failures, neither on the tip of the master branch, nor on the commit when these lines were introduced.
So either you should explain to me what it's all about, or I'll have to submit a pull request and remove them.
I'm still going to explore the git options further, and I might find that I'm wrong.

[al-the-x]

You might try rewinding your local copy of the project to that point in
time and looking around at the calling code to see how it was being used
when the variadic arguments were added. If indeed that's dead code now, a
PR to remove it would be valuable to the project. If it's not dead, opening
a PR to remove it might reveal where its used. Just running the tests
doesn't imply coverage of that code nor even full coverage.

[pomerantsev]

I did that, too, but again, I haven't seen a single place in the code where invoke would be called with a string argument in the third position.
So I'd say it's been dead code from the get-go (maybe it meant something initially, but it should have been removed when the commit was squashed).
Anyway, I'll make a PR, and we can discuss it on Monday.
The other thing I haven't understood in this task is the --word-diff option. I could not figure out how it should be used, and using git log with and without this option yielded the same results.

[pomerantsev]

PR and discussion: angular/angular.js#8273

[al-the-x]

Great job. The --word-diff option changes the display of diffs / patches from line-wise differences to word-wise differences. For example, if I changed the name of a function or its arguments, by default git will show the entire line as being changed, even if I just corrected a typo (I will never again name a function receive). With --word-diff, git will more intelligently show that only the name changed, not the whole line. Useful for tracking down when an argument was added, too.

[pomerantsev]

Thanks. I was able to see something meaningful with --word-diff now.

[pomerantsev]

Another question: how to search for a