git-blame shows what revision and author last modified each line of a file.
$ echo "this is a test" > test.txt
$ git add test.txt
$ git commit -m "first commit"
$ git blame test.txt
^d12054e (John Doe 2023-07-20 10:08:32 -0300 1) this is a test
If a codebase needs a major cosmetic change like fixing the formatting (e.g. terraform fmt -recursive, black, etc.), that commits is going to make tracking changes harder because it shadows all previous commits:
$ vi test.txt # change file in non-functional way (e.g. fix formatting only)
$ git add test.txt
$ git commit -m "second commit (format only, no functional changes)"
[main a7b7f21] second commit (format only, no functional changes)
1 file changed, 1 insertion(+), 1 deletion(-)
$ git blame test.txt
a7b7f214 (John Doe 2023-07-20 10:10:47 -0300 1) this is a test
git-blame shows the last commit a7b7f214 (formatting only) and it's usually not very productive when you want to see what really changed in that file.
One way to overcome this situation is to tell git-blame to ignore certain commits. This is done through the configuration option config blame.ignoreRevsFile:
Add the commit SHA to a file that will hold all commits that are ignored by git-blame:
$ echo "a7b7f214539c875b6aa18b68f65186d07ae008fb # Major formatting fix" >> .gitblameignore
$ git config blame.ignoreRevsFile .gitblameignore
Notice that git-blame now ignores commit a7b7f214 and shows the previous one (d12054e):
$ git blame test.txt
^d12054e (John Doe 2023-07-20 10:08:32 -0300 1) this is a test
Notice that the commit still shows in the commit log as usual:
$ git log ./test.txt
commit a7b7f214539c875b6aa18b68f65186d07ae008fb (HEAD -> main)
Author: John Doe <[email protected]>
Date: Thu Jul 20 10:10:47 2023 -0300
second commit (format only, no functional changes)
commit d12054e565c4d1b3a46c0f5c49f4b6c3563ab1a2
Author: John Doe <[email protected]>
Date: Thu Jul 20 10:08:32 2023 -0300
first commit
Since these major reformatting events are rare, it's doable to add the individual commits to the .gitblameignore file whenever needed.