How to get the last commit date for a bunch of files in Git?

Here's a one liner using find (broken into several for readability, but thanks to the trailing backslashes, copy–paste should work):

find <dirs...> -name '<pattern>' <any other predicate to get what you want> \
  -exec git log -1 --format="AAA%ai NNN" '{}' \; \
  -exec echo '{}' XXX \; \
| tr \\n N | sed -e 's/AAA/\n/g' | sed -e 's/NNNN/ /g' -e 's/XXX.*//g'

The overly complex newline mangling with tr and sed is just there to get date and filename on one line, and to ignore untracked files. You have to make sure that none of your files contain those silly markers AAA XXX NNNN.

Use git ls-files to find git files, and then git log to format the output. But since git log will group several file together when they share same commit time, I prefer to have it process one file at a time and then sort the result.

The resulted one-liner:

for f in $(git ls-files); do git --no-pager log --color -1 --date=short --pretty=format:'%C(cyan)%ai%Creset' -- $f ; echo  " $f"; done |sort -r

If you want to add it to your .bashrc:

function gls() {
    for f in $(git ls-files); do git --no-pager log --color -1 --date=short --pretty=format:'%C(cyan)%ai%Creset' -- $f ; echo  " $f"; done |sort -r
}

Then running gls will output something like:

2019-09-30 11:42:40 -0400 a.c
2019-08-20 11:59:56 -0400 b.conf
2019-08-19 16:18:00 -0400 c.c
2019-08-19 16:17:51 -0400 d.pc

The result is in time descending order.

The following command will be helpful:

git log -1 --format=%cd filename.txt

This will print the latest change date for one file. The -1 shows one log entry (the most recent), and --format=%cd shows the commit date. See the documentation for git-log for a full description of the options.

You should be able to easily extend this for a group of files.

Slightly extending Greg's answer, git log can take multiple paths in its argument. It will then show only the commits which included those paths. Therefore, to get the latest commit for a group of files:

git log -1 --format=%cd -- fileA.txt fileB.txt fileC.txt

I'm pretty rubbish at shell scripting, so I'm not exactly sure how to construct that command via piping, but maybe that'd be a good topic for another question.