Glossary
- Blobs = The way git stores files. Can be retrieved by its unique hash
- Tree = The way git stores directories. Can be retrived by its unique hash
- Index = Staging = Cache = temporary storage holding the trees and blobs to commit
- Ref-log = local (no shared with upstream) log of
- Plumbing/Porcelain commands = internal/user facing commands
Commit/Tree-ish
- Commit-ish : every expression that can be resolved into a node in the version tree
- Tree-ish : a commit-ish followed by a path. A commit-ish is a tree-ish to the root
-
@ operator only works with the ref-log
D F <-- master <-- HEAD \ / \ \ / | \ / | topic --> B C \ / \ / A
| Commit-ish | Resolves to |
|---|---|
HEAD |
F (the branch HEAD is currently pointing to) |
HEAD^ = HEAD^1 = HEAD~ = HEAD~1 |
B (HEAD’s first parent) |
F^2 |
C (F’s second parent) |
D~~ = D~2 = D^^ |
A (2 past generation first ancestor) |
refs/head/master = head/master = master |
F (master branch tip) |
HEAD@{1 days ago} |
B (yesterday you were working on the topic branch) |
:/commit\_msg |
The youngest matching command from ANY ref commit matching message |
Revision ranges
A---B---C topic
/
D---E---F---G master
| Revision range | Resolves to |
|---|---|
B |
D, E, A, B (all commits reachable from B) |
B^@ |
D, E, A (all commits reachable from B, except himself) |
C G |
ALL (commits reachable from both C and G) |
G ^C = C..G (double dot) |
G, F (commits reachable by G and NOT by C) |
C...G (triple dot) |
C, B, A, F, G (commits reachable by C or G but NOT both) |
Reset and checkout
A---B---C topic A---B---C topic <- HEAD A---B---C topic
/ (git checkout topic) / (git checkout F) /
D---E---F---G master <- HEAD D---E---F---G master D---E---F---G master
^
HEAD (detached mode)
A---B---C topic A---B---C topic <- master <- HEAD
/ (git reset topic) /
D---E---F---G master <- HEAD D---E---F---G <- Orphan branch (may be cleaned on garbage collection)
| Reset/Checkout command | Branch ref | Index | Working directory |
|---|---|---|---|
git reset --soft <commit-ish> |
<commit-ish> | NO change | NO change |
git reset --mixed <commit-ish> |
<commit-ish> | <commit-ish> | NO change |
git reset --hard <commit-ish> |
<commit-ish> | <commit-ish> | <commit-ish> |
git reset --mixed <path> (cannot accept a commit-ish) |
N/A | <commit-ish> | NO change |
git reset --hard <path> (cannot accept a commit-ish) |
N/A | <commit-ish> | <commit-ish> |
git checkout <commit-ish> (like reset hard with exceptions) |
<commit-ish> | <commit-ish> | <commit-ish> |
git checkout <commit-ish> <path> |
NO change | NO change (unless path is staged) | reverts <path> to <commit-ish> |
.git directory
- .git/refs : contains the commit hashes for the different local/upstream branches and tags
- .git/objects : stores blobs, trees and packs in a content addressable filesystem (the object hash = path)
- .git/logs : contains the ref-log for the different branches
- .git/HEAD : a simple file with the name of the ref HEAD currently points to (eg: refs/heads/master)
Rebasing branches
F---G topic <- HEAD D---E branch
/ /
D---E branch (git rebase master) / D'---F'---G' topic <- HEAD
/ / /
A---B---C master A---B---C master
F---G topic <- HEAD D---E branch
/ /
D---E branch (git rebase --onto master branch topic) / F'---G' topic <- HEAD
/ / /
A---B---C master A---B---C master
F---G alien A'---B'---C' branch <- HEAD
(git rebase --root --onto alien) /
D---E branch or F---G alien
/ (git rebase alien)
A---B---C master <- HEAD A---B---D---E branch
- Notice the rebased commits are brand new, they all have a different hash
Interesting commands
stash pop|list: stores the contents of the working directory away andreset --hard. You can restore usingstash popshow -p <revision-range>: outputs a patch file with the changes in all commits in <revision-range>cherry-pick <revision-range>: applies all changes in <revision-range> on top of HEAD. It creates new commits not linked to the rangemerge --strategy=recursive -Xours <branch>: merges with <branch>, attempts to solve merge to the same files, but defaults to HEAD’s branch in case of conflictslog --branches --before=2015-12-25 --after=2015-11-26: displays all commits between the 2 dates for ALL branches
.git/config and remotes
