ignoring changes matching a string in git diff

Question

I\'ve made a single simple change to a large number of files that are version controlled in git and I\'d like to be able to check that no other changes are slipping into thi

Answer 1

No more grep needed!

With Git 2.30 (Q1 2021), "git diff"^(man) family of commands learned the "-I<regex>" option to ignore hunks whose changed lines all match the given pattern.

See commit 296d4a9, commit ec7967c (20 Oct 2020) by Michał Kępień (kempniu).
^{(Merged by Junio C Hamano -- gitster -- in commit 1ae0949, 02 Nov 2020)}

diff: add -I<regex> that ignores matching changes

^{Signed-off-by: Michał Kępień}

Add a new diff option that enables ignoring changes whose all lines (changed, removed, and added) match a given regular expression.
This is similar to the -I/--ignore-matching-lines option in standalone diff utilities and can be used e.g. to ignore changes which only affect code comments or to look for unrelated changes in commits containing a large number of automatically applied modifications (e.g. a tree-wide string replacement).

The difference between -G/-S and the new -I option is that the latter filters output on a per-change basis.

Use the 'ignore' field of xdchange_t for marking a change as ignored or not.
Since the same field is used by --ignore-blank-lines, identical hunk emitting rules apply for --ignore-blank-lines and -I.
These two options can also be used together in the same git invocation (they are complementary to each other).

Rename xdl_mark_ignorable() to xdl_mark_ignorable_lines(), to indicate that it is logically a "sibling" of xdl_mark_ignorable_regex() rather than its "parent".

diff-options now includes in its man page:

-I<regex>

--ignore-matching-lines=<regex>

Ignore changes whose all lines match <regex>.
This option may be specified more than once.

Examples:

git diff --ignore-blank-lines -I"ten.*e" -I"^[124-9]"

Answer 2

Use git difftool to run a real diff.

Example: https://github.com/cben/kubernetes-discovery-samples/commit/b1e946434e73d8d1650c887f7d49b46dcbd835a6
I've created a script running diff the way I want to (here I'm keeping curl --verbose outputs in the repo, resulting in boring changes each time I rerun the curl):

#!/bin/bash
diff --recursive --unified=1 --color \
     --ignore-matching-lines=serverAddress \
     --ignore-matching-lines='^\*  subject:' \
     --ignore-matching-lines='^\*  start date:' \
     --ignore-matching-lines='^\*  expire date:' \
     --ignore-matching-lines='^\*  issuer:' \
     --ignore-matching-lines='^< Date:' \
     --ignore-matching-lines='^< Content-Length:' \
     --ignore-matching-lines='--:--:--' \
     --ignore-matching-lines='{ \[[0-9]* bytes data\]' \
     "$@"

And now I can run git difftool --dir-diff --extcmd=path/to/above/script.sh and see only interesting changes.

An important caveat about GNU diff -I aka --ignore-matching-lines: this merely prevents such lines from making a chunk "intersting" but when these changes appear in same chunk with other non-ignored changes, it will still show them. I used --unified=1 above to reduce this effect by making chunks smaller (only 1 context line above and below each change).

Answer 3

Try the following:

$ git diff > full_diff.txt
$ git diff -G "your pattern" > matching_diff.txt

You can then compare the two like so:

$ diff matching_diff.txt full_diff.txt

If all changes match the pattern, full_diff.txt and matching_diff.txt will be identical, and the last diff command will not return anything.

If there are changes that do not match the pattern, the last diff will highlight those.

---

You can combine all of the above steps and avoid having to create two extra files like so:

diff <(git diff -G "your pattern") <(git diff)  # works with other diff tools too

Answer 4

I think that I have a different solution using pipes and grep. I had two files that needed to be checked for differences that didn't include @@ and g:, so I did this (borrowing from here and here and here:

$ git diff -U0 --color-words --no-index file1.tex file2.tex | grep -v -e "@@" -e "g:"

and that seemed to do the trick. Colors still were there.

So I assume you could take a simpler git diff command/output and do the same thing. What I like about this is that it doesn't require making new files or redirection (other than a pipe).