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diff --git a/users/wpcarro/website/blog/posts/git-filter-repo-note.md b/users/wpcarro/website/blog/posts/git-filter-repo-note.md new file mode 100644 index 000000000000..e5fbb05f5cd2 --- /dev/null +++ b/users/wpcarro/website/blog/posts/git-filter-repo-note.md @@ -0,0 +1,59 @@ +## Background + +- I recently used `git-filter-repo` to scrub cleartext secrets from a + repository. +- We pin some services' deployments to commit SHAs. +- These commit SHAs are no longer reachable from `origin/main`. + +## Problem + +If `git` garbage-collects any of the commits to which services are pinned, and +that service attempts to redeploy, the deployment will fail. + +`git for-each-ref --contains $SHA` will report all of the refs that can reach +some commit, `$SHA`. This may report things like: +- `refs/replace` (i.e. `git-filter-repo` artifacts) +- `refs/stash` +- some local branches +- some remote branches + +One solution might involve creating references to avoid garbage-collection. But +if any of our pinned commits contains sensitive cleartext we *want* to ensure +that `git` purges these. + +Instead let's find the SHAs of the new, rewritten commits and replace the pinned +versions with those. + +## Solution + +Essentially we want to find a commit with the same *tree* state as the currently +pinned commit. Here are two ways to get that info... + +This way is indirect, but provides more context about the change: + +```shell +λ git cat-file -p $SHA +tree d011a1dd4a3c5c4c6455ab3592fa2bf71d551d22 # <-- copy this tree info +parent ba88bbf8de61be932184631244d2ec0ec8205cb8 +author William Carroll <wpcarro@gmail.com> 1664993052 -0700 +committer William Carroll <wpcarro@gmail.com> 1665116042 -0700 + +feat(florp): Florp can now flarp + +You're welcome :) +``` + +This way is more direct (read: code-golf-friendly): + +```shell +λ git log -1 --format=%T $SHA +``` + +Now that we have the SHA of the desired tree state, let's use it to query `git` +for commits with the same tree SHA. + +```shell +λ git log --format='%H %T' | grep $(git log --format=%T -1 $SHA) | awk '{ print $1 }' +``` + +Hopefully this helps! |