static-site-pipeline/hugo/content/posts/2023-09-06-git-showcase.md

lastmod, author, categories, date, title, summary

lastmod	author	categories	date	title	summary
2023-09-06T13:51:00.0000000+01:00	patrick	programming	2023-09-06T13:51:00Z	Notes for a Git fireside chat	A syllabus for a fireside chat to give at work, on Git

This is simply an outline, with no actual content.

How Git works

• Recommendation to read Pro Git
• Fundamental model: the object database
  • Blobs, trees, tags, commits
• Extra metadata
  • Branches
  • Lightweight tags
  • HEAD (and other symbolic refs)
  • Remotes
• Mention of performance optimisations such as packfiles
• Merge algorithms
  • recursive
  • ort
  • ours
• Useful commands
  • git rev-parse
  • git merge-base
  • git symbolic-ref
  • git clone --depth=1
  • git commit --amend
  • git grep (although ripgrep is generally faster anyway)
  • git log -p (for patch) and -S function_name
  • git blame
• Brief mention of what a submodule is
• Brief mention of what git rebase is
• How-tos
  • Stacked PRs in a squash-merge-to-main world
• Case studies
  • $INTERNAL_WORKSPACE_TOOL push-files
  • my internal Git-related dotfiles
  • git-appraise

Problems with Git, and why Pijul is interesting

Merging

Git works on snapshots => merging is impossible in principle. Here's the textbook example:

Start:

A
B

Branch 1:

A
X
B

Branch 2:

G
A
B

then

A
B
G
A
B

When merging branch 1 and branch 2, the snapshot-based merge algorithm can't know which AB pair the X was added in between, so it must choose arbitrarily.

Conflicts

Conflicts are not modelled at all: a conflict is only a property of the working tree, and you can't "commit it". That means you can never tell Git how to resolve a conflict in such a way that it can reliably resolve the same conflict again in the future. (git rerere is a hack that in my experience frequently does not do the right thing.)