Posted about 1 month ago. Visible to the public.

Git: Parsing large diffs as a human

I just finished migrating a project from the Asset Pipeline to Webpacker, this is what my diff to master looks like:

5.825 files changed, 44.805 insertions(+), 529.948 deletions(-)
warning: inexact rename detection was skipped due to too many files.
warning: you may want to set your diff.renameLimit variable to at least 5134 and retry the command.

There is no way me or my peer reviewer is able to parse 500k+ lines of code. Fortunately, git has some handy diff options ready:

option comment
--color-moved=dimmed_zebra Highlight only changes in renamed files
--find-renames=X% Default: 50%. If not all renames are matched, use a smaller amount.
--diff-algorithm Try out different algorithms if the diff doesn't look right
--no-color-moved-ws Hides white-space changes for moved files
--diff-filter=X Restrict diff to: Added (A), Copied (C), Deleted (D), Modified (M), Renamed (R), Unknown (X) files

To tackle the rename limit mentioned above, update the local or global git configuration.

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git config diff.renameLimit 9999

Furthermore, I encourage you to further split the diff into smaller chunks:

  • By file extension (e.g.: first review your Ruby code, then JS, then the rest)
  • By excluding directories (e.g.: handle application and vendor code separately)

Overall I ended up splitting up my code into these (human readable) chunks:

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git diff master --color-moved=dimmed_zebra --find-renames=25% '*.sass' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% '*.coffee' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% '*.js' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% '*.haml' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% '*.rb' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% ':!*.coffee' ':!*.sass' ':!*.js' ':!*.haml' ':!*.rb' ':!vendor' git diff master --color-moved=dimmed_zebra --find-renames=25% vendor/

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Owner of this card:

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Michael Leimstädtner
Last edit:
about 1 month ago
by Michael Leimstädtner
About this deck:
We are makandra and do test-driven, agile Ruby on Rails software development.
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Posted by Michael Leimstädtner to makandra dev
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