How to get git log to show tags, greppably?

Question

I've been having a surprisingly hard time getting git log to show tags. I thought I'd found the answer here, but I've just discovered that when I do

git log --tags --no-walk | grep a-tag-pattern-I'm-looking-for

it doesn't work.

In fact it looks like the --tags and --no-walk options are red herrings for my purposes. Plain

git log

does show tags, but

git log | grep a-tag-pattern-I'm-looking-for

does not.

I think I can see what's going on: when git log's output is a terminal, it colorizes tag names differently. But when the output is a pipe, it appears that it not only turns off the colorization, it doesn't output the tag annotations at all.

Can anyone suggest a way to get git log to show tags in its output, even when its output is a pipe?

git version 2.20.1, if it matters.

Answer 1

As an aside that's too long for a comment, git rev-list is the core command, the "plumbing", underlying basically all the conveniences that accept a list of revisions.

It's not apparent in the v2.20 git log docs but it, like basically every command that operates on a generated list of commits, uses git rev-list's machinery to generate that list and takes all its options.

git log --tags=$yourpattern

has (I think and did some quick checks) always worked, Git just expected people to somehow know it would. Like an easter egg or something :-/. Which I did, once you see how it's put together, the convenience commands starting as (often quite obvious and short) scripts for common core command sequences, you learn: this is doing handy things with rev-list, that's doing handy things with read-tree, la la. It was one of those things people just imbibed, it was (and I'm not even sure how) clear to people who learned about Git by following a particular path.

Answer 2

The problem turned out to be related to the --decorate option. Those tags I wanted to see are listed only with git log --decorate=short or git log --decorate=full.

With git log --decorate=auto, however, they're shown only if the output is going to a terminal, meaning they were suppressed when I piped git log's output to grep.

Compounding the difficulty is the fact that the help text was inaccurate in some versions, wrongly claiming that the default value for --decorate was short. But the more up-to-date documentation says:

If auto is specified, then if the output is going to a terminal, the ref names are shown as if short were given, otherwise no ref names are shown. The option --decorate is short-hand for --decorate=short. Default to configuration value of log.decorate if configured, otherwise, auto.

So I ran

git config --global --add log.decorate short

to globally set the default for git log --decorate to short, and now I can run both

git log

and

git log | grep …

and see tags and other output consistently.