Please do this. The one thing I miss most about phabricator is that it can differentiate between moved vs actually changed code.

Yup, now I'm discouraged to move code blocks into separate files, because the actual change info is lost with the moving of a code block. even though it's nicer in the long run. No one in my team does this in favor of clear PR's, but we do end up with long files for this reason.

(Crossposted to https://gist.github.com/0xdevalias/1245fe66ac6953d490114b417a0075e3 for posterity)

Omg yes, please! This is one of my biggest pet peeves/code review slowdowns when performing large refactors to cleanup a legacy codebase.

The following were some manual review notes/commands I added to a recent PR to assist others who were reviewing:

The following git diff command will make it easier to see what actually changed in the code here, as opposed to what just moved around without being changed; to make review/etc easier. Dimmed code in the diff has been moved, but not changed.

This will get all the changes made in this branch, using devalias/improve-first-use as the base:

git \
  -c color.diff.oldMoved="white dim" \
  -c color.diff.oldMovedAlternative="white dim" \
  -c color.diff.newMoved="white dim" \
  -c color.diff.newMovedAlternative="white dim" \
  -c color.diff.newMovedDimmed="white dim" \
  -c color.diff.newMovedAlternativeDimmed="white dim" \
  diff --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space --minimal \
  devalias/improve-first-use HEAD

This will get all changes made for a specific commit hash (55a259f), as compared to the commit hash just before it (55a259f~):

git \
  -c color.diff.oldMoved="white dim" \
  -c color.diff.oldMovedAlternative="white dim" \
  -c color.diff.newMoved="white dim" \
  -c color.diff.newMovedAlternative="white dim" \
  -c color.diff.newMovedDimmed="white dim" \
  -c color.diff.newMovedAlternativeDimmed="white dim" \
  diff --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space --minimal \
  55a259f~ 55a259f

This will get all changes made for a specific commit hash (55a259f), as compared to the commit hash just before it (55a259f~), only for the specific file/path specified:

git \
  -c color.diff.oldMoved="white dim" \
  -c color.diff.oldMovedAlternative="white dim" \
  -c color.diff.newMoved="white dim" \
  -c color.diff.newMovedAlternative="white dim" \
  -c color.diff.newMovedDimmed="white dim" \
  -c color.diff.newMovedAlternativeDimmed="white dim" \
  diff --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space --minimal \
  55a259f~ 55a259f -- oauth/vendor/slack/index.js

You can simplify this for future use by adding it to your git aliases in your ~/.gitconfig, something like the following:

[alias]
  diff-refactor = \
    -c color.diff.oldMoved='white dim' \
    -c color.diff.oldMovedAlternative='white dim' \
    -c color.diff.newMoved='white dim' \
    -c color.diff.newMovedAlternative='white dim' \
    -c color.diff.newMovedDimmed='white dim' \
    -c color.diff.newMovedAlternativeDimmed='white dim' \
    diff --ignore-blank-lines --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space --minimal

Which would then allow you to use it as just:

⇒ git diff-refactor

⇒ git diff-refactor devalias/improve-first-use HEAD

⇒ git diff-refactor 55a259f~ 55a259f

⇒ git diff-refactor 55a259f~ 55a259f -- oauth/vendor/slack/index.js

You could potentially add the following as well, though i'm not sure if they will do anything new/useful when combined with --color-moved:

--ignore-all-space --ignore-space-change --ignore-space-at-eol --ignore-cr-at-eol --ignore-blank-lines

As an alternative, you can use VS Code to review while highlighting moved code. It's available behind an experimental flag. It also works in githubs online version. So, simply press . in an open PR and review there. Announcement of the feature: https://code.visualstudio.com/updates/v1_82#_moved-code-detection

This would save a ton of time and make code review and refactors easier! I often comment across lines saying “these lines were moved but unchanged” but this doesn’t scale well at all