How do you make `git grep` output look like `ack` output?

Question

I've recently found git grep and come to like its speed and de facto searching of only the files in the repo. But coming from ack (ack-grep in Ubuntu), one thing left to be desired is the output formatting, which is unfortunately much more like grep than ack. Go figure.

ack:

1. Prints the matching filename on the first line by itself.
2. Color highlights the matching filename a bold green.
3. Prints the line number, and only the line number, with each matching line.
4. Color highlights the line number a bold yellow.
5. Color highlights each matching string a background yellow.
6. Prints a blank line between matches from different files.

On the other hand, git grep:

• Prints the filename on every matching line.
• Prints no line number.
• Prints no blank line between matches from different files.
• Color highlights only the matching text, a bold red.

Is there any set of git grep options, or combo with other tools, that can make git grep output look like ack output?

Answer 1

You've already answered part of your own question (--break inserts a blank line between files, --heading prints the file name separately, and -n or --line-number gives you line numbers on each line).

The rest is just color options, which are set in git config via the color.grep.<slot> entries. See the documentation for full details, but note that based on what you asked for, I think this does the trick:

[alias]
    ack = -c color.grep.linenumber=\"bold yellow\" \
          -c color.grep.filename=\"bold green\" \
          -c color.grep.match=\"reverse yellow\" \
          grep --break --heading --line-number

(this is expressed as you'd see it in git config --global --edit since the quoting is messy).

Or, to set it up in one command:

git config --global alias.ack '-c color.grep.linenumber="bold yellow"
    -c color.grep.filename="bold green"
    -c color.grep.match="reverse yellow"
    grep --break --heading --line-number'

Add or subtract -c options to change whatever colors you like, and/or set them to your preferred defaults by setting color.grep.<name> = color instead of using the git ack alias.