Git under the hood

JIT.md

commit

Made of:

• a tree: PWD state, not a diff, but rather an efficient representation of the full state
• a comment
• commiter info
• hash of parent commit Process:
• if file didn't change: add compressed filename (hash) to the snapshot
• if file changed: compress it, store it in .git/objects, add filename hash to snapshot

.git/objects

Q. What is an object? A. a commit, tree, blob

git cat-file -p

pretty print a git object

$ git cat-file -p <tree-hash>
obj-type-code+perms obj-type obj-hash <filename> 
100644              blob     <hash>   world.txt

blobs

stored as the deflated: blob <blob-length><null-char><blob>

trees

stored as the deflated: tree <tree-length><null-char>FOREACH object<mode> <filename><object id in hex>

commits

stored as the deflated:

commit <commit-length><null-char>tree <tree-hash>\
author <author-name> <author-email> <timestamp>\
commiter <commiter-name> <commiter-email> <timestamp>\

<commit-msg>

ids or hashes

SHA1 of <obj-type> <obj-size><null-char><obj>

foo