===== Overview =====

 A small sample of Git revisions; different ways to refer to commits (using Linux kernel source repo).

===== Basic Git revisions =====

''HEAD'' (commonly the default) refers to the commit at the tip of the current branch:

<code>
$ git show
$ git show HEAD
</code>

Commits are also reflected in branch or tag names:

<code>
$ git show master
$ git show v4.16
</code>

And of course you can always use the full commit ID (or a sufficient prefix):

<code>
$ git show 0adb32858b0bddf4ada5f364a84ed60b196dbcda
$ git show 0adb32858b0
</code>

You can use ''git rev-parse'' to map a reference to its underlying commit ID:

<code>
$ git rev-parse v4.16
3fb78e8be9d9428fbc4c016f8b031b01a6fdd63d
$
</code>

===== Ancestral Git revisions/references =====

Given any revision, you can refer to its (first) parent, or first grandparent, and so on:

<code>
$ git show HEAD
$ git show HEAD^         (first parent)
$ git show HEAD^^        (first grandparent)
$ git show master^       (master's first parent)
$ git show v4.16^^^      (v4.16's first great-grandparent)
</code>

There's also the //tilde// notation for brevity, so these are (ignoring intermediate merge commits) equivalent:

<code>
$ git show v4.16^^^
$ git show v4.16~3
</code>

Examples using ''git diff'':

<code>
$ git diff v4.16^^ v4.16^
$ git diff v4.16^ v4.16
</code>

===== Commits with more than one parent =====

First or second parent:

<code>
$ git show HEAD^
$ git show HEAD^2
</code>

Getting carried away:

<code>
$ git show v4.19^2~3^^
</code>