git blaming diffFilter

blaming-diff-filter filters git-diff output and prefixes line information with blamed commit-IDs. When used for interactive.diffFilter, this allows the user during git-add -p to select hunks when creating fixup commits.

Inspiration from git diff-blame.

Using wrapping filters

Optionally, an additional inner filter can be specified to pretty-print the diff. The inner filter receives the raw diff, and blaming-diff-filter applies commit-ID prefixes to the output of the inner filter.

This allows combining it with other fancy highlighting, such as from delta.

Limiting blame history

Using git-blame-filter is useful in topic branches to edit commits not yet in an integration branch (such as main, master or dev) by creating fixup! commits. When doing so, blaming diff lines beyond that integration branch is not helpful, as one usually does not want to create fixups versus commits in the integration branch.

Blaming diff lines therefore can be limited to commits that are not in the integration branch using the --back-to/-b option. This is done by finding the best common ancestor of that branch and HEAD (the topic branch), and then blame only up to that ancestor. Lines that do not come from commits in the topic branch are annotated as ······, increasing visibility of useful commit-IDs significantly. As an extra, this may speed up blaming on large projects.

Listing candidate commits

Annotated commits can be printed with additional information to stderr using a custom git format-string. This allows giving some context to the user during git add -p, so the candidate commits are known.

The -f/--format option takes a git format-string as given to the git-show --format= option. It may take any format specifiers, including colors.

Configuration

Example git-config:

[alias]
    diff-blame = !git diff --color | blaming-diff-filter -- delta --color-only
[interactive]
    diffFilter = blaming-diff-filter -b master -f '%h %s' -- delta --color-only

To create fixup commits, run git add -p, stage hunks for a fixup, then do a git commit --fixup=<commitid>, optionally followed by an interactive rebase.