I’d love Git to grok MS Office docs, but it doesn’t really. It came up again today at work, and coincidentally in Disqus comments for an older blog entry of mine The rise of version control

Anyway, I though I’d spike what Git would do, were it reworked to silently unzip (for commit) and rezip (as it makes working copy). Here’s a repo - git-word-diff-test. Here’s a commit of a simulated storage of a Word doc (Mac Office ) - Mary.docx - which just contains one word per line “Mary had a little lamb”, and a single commit that changed that to “Karl had a little iPad”.

Turns out the commit is pretty noisy - search in page for “iPad”. It was the only intended change. It’s a shame that a whole bunch of random and temporal stuff changes at the same time. Microsoft: try to make idempotent things please.

Never mind, the second commit was only an 170 byte addition to the .git/ blobs, when the .docx file is ordinarily 23Kb in size.

Byte diff calc for the HEAD commit:

COMMITSHA=$(git log | grep "commit " | head -n 1 | sed 's/commit //')
CURRENTSIZE=$(git ls-tree -lrt $COMMITSHA | grep blob | sed -E "s/.{53} *([0-9]*).*/\1/g" | paste -sd+ - | bc)
PREVSIZE=$(git ls-tree -lrt $COMMITSHA^ | grep blob | sed -E "s/.{53} *([0-9]*).*/\1/g" | paste -sd+ - | bc)
echo "$CURRENTSIZE - $PREVSIZE" | bc

(modified from stackoverflow)

As I sorta said in the Disqus comments, I’d pay for Git to be changed to silently unzip .docx, .xlsx and .pptx documents and only reconstitute them in the working copy as I checkout. I’m only interested in the carriage-return-delimited text diffs (incl XML), if I’m diffing at all. Diffs on the binary aspects of zips are a wrong as an operating system not being Unix derivative despite what Cosmin says.

Updates

Sept 1st, 2015

Inside the zip, there’s vbaProject.bin for Word/Excel/Ppowerpoint docs that have VBA. This raises the bar on the idea - as it is binary. Luckily there is open-source know-how that will allow this otherwise less-than-open-standard piece to be unpacked too: Philippe Lagadec’s oletools.

Jul 13th, 2016

I discovered Followup: Managing EXCEL with git - diff problem - a preexiting conversation on the Git mail list, around the same problem.



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July 30th, 2015
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