commit sync post

content/blog/2022-05-18-commit-sync.md

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+---
+layout: page
+title: "Commit syncing across hosted GIT instances" 
+description: "How I keep my commit graph alive"
+date: 2022-05-18
+tags: random
+draft: false
+extra:
+  uses_katex: true
+  auto_center_images: true
+  excerpt: This post covers how to keep your commit graph alive across multiple GIT instances by syncing your commit history to magic repos.
+---
+
+Since September of 2018 (3 and a half years ago) I have been roughly holding a streak of going no more than three days without making a commit to some project on GitHub.
+
+![A screenshot of my commit history last year](/images/posts/commit-sync/commit_graph.png)
+
+This is not entirely intentional, and I have broken it a few times:
+
+- June 7, 2019
+- August 8, 2019
+- September 27, 2019
+- November 3, 2021
+
+..but a streak is a streak. A few of my friends know about this and keep an eye on my commit graph and I do too. Recently, with most of my programming time allocated to work, my graph started looking like weeks of empty cells, implying I broke my streak for good.
+
+In reality, that couldn't be farther from the truth. I have been writing quite a lot of code actually, its just all tracked in a company GIT instance with a separate account.
+
+## Time for some trickery
+
+I happened to remember a little trick I used in a CI pipeline for [Raider Robotics](https://github.com/frc5024/) where you can backdate empty commits with arbitrary authors. I recall using this for some kind of version tagging system at some point.. idk.. the important part being it is possible to make "fake" commits with the right command-line flags.
+
+### The game plan
+
+My idea was as follows:
+
+1) Scrape all work repos for commits authored by one of my email addresses
+2) Keep track of the commit timestamps
+3) Make empty commits to a GitHub repo and backdate them to the timestamps from the last step
+4) Enjoy having my GitHub contributor graph synced to my work account
+
+*For anyone concerned with the security issue of leaking commit data, In my real implementation, dates are shuffled a bit. This also all happens in a private repo, so the public can only ever see its affect on my commit graph, and can't actually see the commits themselves.*
+
+### Scraping commits from repos
+
+The `git` command has a `log` subcommand for querying info about commits. In its simplest form, you can dump all commits for a repo with:
+
+```sh
+git -C /path/to/repo log --pretty=format:"%H"
+```
+
+An example output for the repo behind this website:
+
+```text
+...
+62d0c4833766671182ed0aeeb76bb16cc3f35174
+420b3cc4a9d61024e0dd6c32deafb57244d09433
+fed6fc374d02c2ae8f67bff837c8c8334760b303
+5a64788339afd750c3853468f89d275cf8fa49cd
+01992912951d80631fa5069fce7d9a3593bbcd39
+d894387400158d231ed6559636169f1464bb630d
+4a68456c7a5df699bc7620c9250b7a04aac5bd3c
+ff87809b9c14c5132ecd5a39921b1cf2118b12cc
+2b8797bbdcec61654540d995aaae67bcab8dc1c1
+c4d978c5d098846b8a0105c5b6d3f42b389c6ea7
+9791cdd979a17f0d5ebf9028d4778152ca07ae1d
+dda08261872d3c2301cc02108c0f466dedaacaca
+f408c1fa9785a40038e04b0ef017bd8d2897cdd6
+...
+```
+
+Its just a bunch of hashes.
+
+As a side note, if you are trying to replicate my work and also commit with multiple email addresses, you can chain `--author` flags together.
+
+```sh
+git -C /path/to/repo log --pretty=format:"%H" --author=ewpratten@example.com --author=evan@work.com
+```
+
+### Cloning commits
+
+If we iterate over our list of hashes, we can perform the rest of the steps. The main data point we care about is the timestamp.
+
+To fetch a commit timestamp from a repo, use the following, replacing `$COMMIT_HASH` with the hash in question:
+
+```sh
+git -C /path/to/repo show -s --format=%ci $COMMIT_HASH
+```
+
+And finally, with our timestamp (stored as `$DATE`) a new commit can be written to a target repo:
+
+```sh
+git -C /path/to/public/repo commit -m "A message." --date="$DATE" --no-edit --allow-empty
+```
+
+Importantly, the `--allow-empty` flag removes the requirement for any files to be contained in the commit, essentially allowing you to have a "zero size" repository.
+
+## Conclusion
+
+Uh, ya. Cool. With your scripting language of choice, you can chain these commands together, toss a `git push` in there, stick this in a cron job, and have yourself a nice, healthy commit graph.
+