Git Help Desk

Object Database Layer 🎯

object database, $GIT_COMMON_DIR/objects/ (file system)
alternate object database
<pathspec>

Parameters

Configuration
git version
git config, $GIT_COMMON_DIR/config, $GIT_DIR/config.worktree
{configuration files}
section, subsection, value
types, runtime prefix
include
{configuration scopes}
protected configuration
multiple values
options＞env_vars＞config_vars
{configuration variables}
git var
{logical variables}
CLI
plumbing (core Git)
porcelain
path syntax in output
control characters in output
git
{environment variables}
conventions (options and args)
options＞env_vars＞config_vars
--index⊇--cached＝--staged^--worktree

Managing Objects

Core Data Model
Git for Computer Scientists
object
object name (object identifier, object ID, oid) (SHA-1)
object type
reachable
unreachable object
dangling object
git cat-file
git show
git hash-object
blob object
git grep
git unpack-file
recover-corrupted-blob-object
recover-corrupted-object-harder
tree object
tree (directory)
tree-ish (treeish)
git ls-tree
git mktree
commit object (commit)
commit-ish (committish)
parent
git commit-tree
tag object
git mktag
$GIT_COMMON_DIR/(repository layout), repository format version
$GIT_DIR/index(index format), index (cache), index entry
racy Git problem, racily clean
$GIT_COMMON_DIR/hooks/, hook, git hook
update-hook-example

Managing Working Trees

.git directory gitdir: --git-dir/$GIT_DIR/automatically discovered
root of working tree worktree: --work-tree (git)/$GIT_WORK_TREE/​core.worktree/...
gitfile .git
non-worktree files directory: $GIT_COMMON_DIR
$GIT_DIR vs $GIT_COMMON_DIR: --work-tree (git config), extensions.worktreeConfig, git worktree
worktree = working tree + per-worktree metadata (per-worktree ref + ...)
git worktree, $GIT_DIR: $GIT_COMMON_DIR/worktrees/<id>/, $GIT_DIR/refs/worktree/
main worktree, linked worktree
clean (git read-tree); dirty, stash entry
git stash

Attributes per Path

$GIT_WORK_TREE/**/.gitattributes
pattern
overriding, {configuration files}
macro attribute
git check-attr

Classifying Paths

$GIT_WORK_TREE/**/.gitignore
pattern
overriding, {configuration files}
how to stop tracking tracked and ignored files
how to force tracking not-tracked and ignored files
git check-ignore
$GIT_WORK_TREE/**/.gitkeep
Precious Files Design Document
tracked
present (part of sparse checkout)
not present (not part of sparse checkout)
not tracked
ignored (expendable)
trashable (ignored-and-expendable)
precious (ignored-and-not-expendable)
untracked (not tracked and not ignored) (not expendable)

Source Code Management Layer 🎯

SCM
pseudoref
ref, $GIT_COMMON_DIR/refs/: name pointing to an object name/another ref, has refname and reflog
name pointing to another ref: symref (symbolic reference)
name pointing to an object name (git fetch):
branch's head, $GIT_COMMON_DIR/refs/heads/ (head ref): name pointing to tip of branch
tag, $GIT_COMMON_DIR/refs/tags/, <tag>
...
name pointing to either an object name/another ref:
HEAD, $GIT_DIR/HEAD, HEAD: name pointing to current branch or an arbitrary commit
detached HEAD (git checkout)
unborn branch: caused by git init or orphan operation
...
branch
(local) branch, <head>
remote-tracking branch, $GIT_COMMON_DIR/refs/remotes/
upstream branch (git fetch)

Revision Specification

commit (revision)
Revision Notation (extended SHA-1 syntax), <hash>^{<algo>}
dereference
peel
git rev-parse
▶
◀
git name-rev
git describe
🧪git format-rev
expression
denotation

Managing References

git check-ref-format pattern
git update-ref, $GIT_DIR/logs/
git show-ref pattern
git ls-remote pattern
git for-each-ref
git reflog
git symbolic-ref
git branch
git tag
annotated tag, lightweight tag

Namespaces

(examples)

Repository Creation and Synchronization

git init
🧪git repo
git subtree

Submodules $GIT_COMMON_DIR/modules/

submodule, superproject
$GIT_WORK_TREE/.gitmodules
git submodule
how to force adding a submodule whose path-derived name is occupied
how to completely remove a submodule
git subrepo

Tracked Repositories

git remote
Remote Helpers
git remote-ext
git remote-fd
...

Credentials

git credential
Credential Helpers
git credential-cache
git credential-store
...
repository: object database + refs + meta data
<repository>: URL, name of remote or name of remote group, tracks remote repository/repositories
alternate repository
bare repository (git clone)
mirror
shallow repository (shallow clone), $GIT_COMMON_DIR/shallow
partial clone, promisor remote
<refspec> (git fetch) (git push)
git clone, 🧪git backfill
git fetch, $GIT_DIR/FETCH_HEAD
git pull
git fetch-pack
"thin" pack
◀
git upload-pack
git send-pack
"thin" pack
▶
git receive-pack
quarantine environment
🖳
🖧
git push
status flag
git request-pull
using-signed-tag-in-pull-request
git merge
git fetch
git pull
git push

Snapshotting

git read-tree
sparse checkout, how to repopulate the working directory
git checkout-index
git update-index
refresh
assume unchanged bit
skip-worktree bit, sparse checkout
split index $GIT_DIR/index, shared index file $GIT_DIR/sharedindex
untracked cache
file system monitor
how to ignore tracked files
git write-tree
git checkout
checkout
git switch
git restore
git sparse-checkout
git reset
git clean
git checkout
checkout
overlay/no-overlay
parallel checkout
git switch
git restore
git sparse-checkout
git reset
git add
git rm
git mv
git commit
commit
trailer
git interpret-trailers
DB
index
working tree
│
┌
┐
▼
│
┌
text
ident
filter
┐
▼
│
┘
text
ident
filter
└
▲
│
┘
└
▲
how to publish the tree from a commit without exposing its full history, how to start a disconnected history
git notes, $GIT_COMMON_DIR/refs/notes/, $GIT_DIR/{NOTES_MERGE_PARTIAL,NOTES_MERGE_WORKTREE,NOTES_MERGE_REF}
git replace, $GIT_COMMON_DIR/refs/replace/

Checkin/Checkout Filters

text/binary per file: text/eol/core.autocrlf
line-ending style per text file: eol/core.autocrlf/core.eol
safety net: core.safecrlf
ident
filter driver, clean filter, smudge filter, process filter: filter
diffcore transformation
pickaxe
git diff-tree
git diff-files
git diff-index
DB
index
working
tree
▼
┌
┐
▼
▼
┌
┐
▼
▲
└
▶
┘
└
⌵
┘

Diffing

git ls-files
resolve-undo information
status tag
<eolinfo>, <eolattr>
git status
path syntax in output (git status)
status code
git show
git diff
status letter
git difftool
git range-diff

Listing History

<filter-spec>
git rev-list
path syntax in output (git rev-list)
git log
git shortlog
git show-branch
git blame
🧪git last-modified

Debugging History

git bisect, $GIT_DIR/{refs/bisect/,BISECT_HEAD,BISECT_EXPECTED_REV}
checking whitespace errors per file: whitespace/core.whitespace

Diff Driver (for user facing diff output)

diff driver per file: diff/core.bigFileThreshold
how to mark files as binary to generate binary patch but still use diff drivers (to generate human-readable text diff)
customizing internal diff driver (the builtin diff machinery)
diff algorithm per file: diff.<driver>.algorithm/diff.algorithm
how to define hunk header, built-in patterns: diff.<driver>.xfuncname
how to customize word diff: --word-diff-regex/diff.<driver>.wordRegex/diff.wordRegex
how to perform text diffs of binary files, how to invalidate cache: --[no-]textconv/diff.<driver>.textconv,diff.<driver>.cachetextconv
how to define external diff driver

Diff Filter (mark up the diff further for human consumption)

interactive.diffFilter

Combining Diffs

1-way merge (single tree merge) (git read-tree) (trivial merge)
2-way merge (two tree merge) (git read-tree) (trivial merge)
initial checkout
fast-forward (merge) (git merge)
fast-forward (update) (git push)
3-way merge (git read-tree) (trivial merge)
(true) merge (git merge)
unmerged index entry (git read-tree), unmerged index
stage (git read-tree) (git ls-files) (git merge)
evil merge
merge (merge commit)
non-fast-forward (update) (git push)
octopus (n-way merge)
octopus merge
topic branch
keep-canonical-history-correct
separating-topic-branches
git cherry

Merge Workflow

merge backend (git status)
merge strategies
using-merge-subtree
git merge, $GIT_DIR/{ORIG_HEAD,MERGE_MSG,MERGE_HEAD,MERGE_AUTOSTASH,AUTO_MERGE}
how to merge annotated tag
git merge-base
merge base
criss-cross merge
git merge-tree
git fmt-merge-msg

Cherry-Picking

changeset
git cherry-pick, $GIT_DIR/CHERRY_PICK_HEAD
git revert, $GIT_DIR/REVERT_HEAD
revert-a-faulty-merge
partial merge (Stop cherry-picking, start merging)

Resolving Conflicts

how to resolve conflicts
git rerere
git mergetool
git merge-index
git merge-one-file
git merge-file

Patch Workflow

apply backend
git format-patch
git patch-id
$GIT_WORK_TREE/.mailmap
git check-mailmap
git imap-send
git send-email
git am, $GIT_DIR/ORIG_HEAD
git mailsplit
git mailinfo
git apply

Merge Driver

merge driver per file: merge/merge.default
built-in merge drivers, how to define merge driver

Rewriting History

Rebase
git rebase, $GIT_DIR/{ORIG_HEAD,REBASE_HEAD,rebase-apply}
how to split commits
how to recover from upstream rebase
rebasing merges, $GIT_DIR/refs/rewritten/
🧪git replay
🧪git history
revert-branch-rebase
rebase-from-internal-branch
git filter-branch, $GIT_DIR/refs/original/
git filter-repo

Miscellaneous

Tutorials

(Introduction)
Glossary
FAQ
Everyday
Tutorial 1
Tutorial 2
Core Tutorial
User Manual
Concepts
Workflows

Support/Feedback

git help
git diagnose
git bugreport

Formatting

git stripspace
git column

Security

(Security) (git upload-pack)
cryptographic signature formats,
mergetag, multi-line object header
git verify-tag
git verify-commit

Examples