Rewriting Git history

The other day I made about 30 commits to a project without realizing my editor was adding spaces to the files even though they mostly contained tabs. I really couldn’t care less whether files have tabs or spaces, but consistency is the important thing, so I decided to rewrite my history using git’s filter-tree option.

This command checks out each original revision, and makes the changes specified, then commits that as a new revision. In this case I replace a tab with 4 spaces in every .cs file. I start from origin/master and go up to the currently checked out commit (head):

git filter-branch --tree-filter "find . -name '*.cs' -exec sed -i -e 's/\t/    /g' {} \;" origin/master..HEAD

You can run an arbitrary script (perhaps run it from a different file if it’s longer than this though!). Here’s another example using git diff to check which “.cs” files were new or modified in the range I’m rewriting, which I then pipe to sed and replace a tab with four spaces.

git filter-branch --tree-filter "git diff --name-status master HEAD | egrep ^[AM] | grep .cs | cut -f2 | xargs sed -i \"s/\t/    /g\"" master..HEAD

This one won’t deal well with files that are created anywhere except the first commit. I’ll leave that as an exercise for the reader 😉

About GrahamTheCoder

I'm Graham (the coder). A C# developer based in Cambridge hoping blogging will achieve some or all of the following. Help me organise my thoughts. Practice writing things other than code. Give me a place to refer people to when I'm trying to make a long winded point. I welcome comments and constructive criticism, and hope to look back at my written opinions in the future and laugh at my own naivety.
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