Rewriting a repo to contain the history of just specific files#

I wanted to start a new git repository containing just the history of two specific files from my help-scraper repository.

I started out planning to use git filter-branch for this, but got put off when this StackOverflow thread started talking about the need to understand the differences between macOS sed and regular GNU sed.

That thread also pointed me to git-filter-repo, a really neat Python script that makes this so much easier.

Installing git-filter-repo#

git-filter-repo is written in Python but has zero dependencies on anything else - all you need to do is place the script somewhere on your path.

I ran echo $PATH to check which directories were on my path - one of them is .local/bin - so I decided to put it there:

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cd ~/.local/bin
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wget https://raw.githubusercontent.com/newren/git-filter-repo/main/git-filter-repo
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chmod 755 git-filter-repo

It didn’t work until I ran chmod 755 on it.

Now I can run this:

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% git filter-repo
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No arguments specified.

Confirming the new command is installed!

Rewriting my repository#

The --path option can be used to preserve just the history of specified paths. I ran this:

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cd /tmp
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git clone https://github.com/simonw/help-scraper
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cd help-scraper
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git filter-repo --path flyctl/fly.graphql --path github/github.graphql

The command output was:

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Parsed 132 commits
2
New history written in 0.33 seconds; now repacking/cleaning...
3
Repacking your repo and cleaning out old unneeded objects
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HEAD is now at 828a1efc GitHub: Tue Mar 22 15:09:04 UTC 2022
5
Enumerating objects: 144, done.
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Counting objects: 100% (144/144), done.
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Delta compression using up to 12 threads
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Compressing objects: 100% (69/69), done.
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Writing objects: 100% (144/144), done.
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Total 144 (delta 34), reused 55 (delta 34), pack-reused 0
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Completely finished after 1.33 seconds.

And sure enough, my repo now only contains those two files:

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% find . | grep -v .git
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.
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./flyctl
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./flyctl/fly.graphql

And the commit history for those files:

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% git log --stat --pretty=oneline | head -n 10
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828a1efc4307cca6cd378c394c2d33eac2eceb52 GitHub: Tue Mar 22 15:09:04 UTC 2022
3
 github/github.graphql | 27 +++++++++++++++++++++++++++
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 1 file changed, 27 insertions(+)
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44fc9ebb49a255ad1c90f7761ab2ab1267135ff9 GitHub: Fri Mar 18 15:08:38 UTC 2022
6
 github/github.graphql | 1 +
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 1 file changed, 1 insertion(+)
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dae52d5b94761145333867bc6641e8210409c3b7 GitHub: Thu Mar 17 16:58:45 UTC 2022
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 github/github.graphql | 3 +++
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 1 file changed, 3 insertions(+)
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33e0691bc579bb1e26ea6d05556cf047f5c120da GitHub: Wed Mar 16 15:05:35 UTC 2022
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help-scraper % git log --stat --pretty=oneline | head -n 20
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828a1efc4307cca6cd378c394c2d33eac2eceb52 GitHub: Tue Mar 22 15:09:04 UTC 2022
14
 github/github.graphql | 27 +++++++++++++++++++++++++++
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 1 file changed, 27 insertions(+)
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44fc9ebb49a255ad1c90f7761ab2ab1267135ff9 GitHub: Fri Mar 18 15:08:38 UTC 2022
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 github/github.graphql | 1 +
18
 1 file changed, 1 insertion(+)
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dae52d5b94761145333867bc6641e8210409c3b7 GitHub: Thu Mar 17 16:58:45 UTC 2022
20
 github/github.graphql | 3 +++
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 1 file changed, 3 insertions(+)
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33e0691bc579bb1e26ea6d05556cf047f5c120da GitHub: Wed Mar 16 15:05:35 UTC 2022
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 github/github.graphql | 54 ++++++++++++++++++++++++++++++++++++++++++++++++---
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 1 file changed, 51 insertions(+), 3 deletions(-)
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3dae87045436c3a8c6c84409f9e7ec5ae3bfae74 GitHub: Tue Mar 15 15:08:59 UTC 2022
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 github/github.graphql | 18 ++++++++++++++++++
27
 1 file changed, 18 insertions(+)
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74a3f34c254f789948ee0257981f5d30a094d19f Fly: Tue Mar 15 06:23:03 UTC 2022
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 flyctl/fly.graphql | 16 ++++++++++++++++
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 1 file changed, 16 insertions(+)
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63c92c60285b08a898b874b9296b28935f0e7ea8 GitHub: Mon Mar 14 15:09:42 UTC 2022
32
 github/github.graphql | 5 ++++-