Inspecting Git repository

The Three Main States

State	Location	Description	Method of inspection
Commited	.git directory	Stored in DB	`git log` `git show` `…`
Modified	Working directory	Changed	`git status` `git diff`
Staged	Staging area (.git/index)	Changed and marked for next commit to the DB	`git status`

Staging area has many names:

Index
Cache
Directory cache
Current directory cache
Staging area
Staged files

Revision

There are many ways to distinguish a specific commit from Git repository.

SHA (hash) - The SHA-1 algorithm is used to create a unique 40-byte hexadecimal string in many corners of git. The SHA (hash-object cat-file)
(refnames, refs)
1. Branch reference (heads) - Branches in Git are nothing more than pointers to the commit. Branch reference is a SHA value of the most recent commit and it is updated with each new commit added. (show rev-parse show-ref)
2. Tag reference - Similar to Branch reference but does not change with new commits. (git describe)
3. HEAD (@) - Note the capital letters. Points to the current commit. (git describe)
4. Other like FETCH_HEAD, MERGE_HEAD, CHERRY_PICK_HEAD, ORIG_HEAD
5. <refname>@{<date>} - For example master@{yesterday}, HEAD@{5 minutes ago}. Note: Date parsing is undocumented but the parser code can be accessed on github.
6. <refname>@{n} - For example master@{7} returns 7th prior commit from master head.
7. <refname>@{-n} - For example @{-2} returns 2nd commit checked out before current one.
8. <branchname>@{upstream} git rev-parse –symbolic-full-name @{u}
9. <rev>^n
10. <rev>~n
11. more …

Walking the tree with ''^'' and ''~''

A =      = A^0
B = A^   = A^1     = A~1
C = A^2  = A^2
D = A^^  = A^1^1   = A~2
E = B^2  = A^^2
F = B^3  = A^^3
G = A^^^ = A^1^1^1 = A~3
H = D^2  = B^^2    = A^^^2  = A~2^2
I = F^   = B^3^    = A^^3^
J = F^2  = B^3^2   = A^^3^2

Tree

(idea taken from here)

</html>

Range

<rev> - ancestors of commit revision
^<rev>
<rev1>..<rev2> - reachable from rev2 but exclude reachable from rev1 (none is HEAD)
<rev1>…<rev2> - reachable from either but not both (none is HEAD)
more …

http://stackoverflow.com/questions/7251477/what-are-the-differences-between-double-dot-and-triple-dot-in-git-dif

Reflog

“Log of references” - list of updates to the references

git reflog

Diff

Show difference between working directory (or index if –cached) and commited.

Merge-Base

Debugging with Git

`blame`	Line-by-line who last modified line
`grep`	Search files for given expression
`bisect`	Manually switch between commits until the one that introduces a chenge is found

References

https://github.com/MaciejKucia/git_tree

Mental Workbench

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