Revision range notations
History traversing commands such as git log operate on a set of commits, not
just a single commit.
For these commands, specifying a single revision, using the notation described in
the previous section, means the set of commits reachable from the given commit.
A commit’s reachable set is the commit itself and the commits in its ancestry chain.
Commit Exclusions
^<rev> (caret) Notation
To exclude commits reachable from a commit, a prefix ^ notation is used. E.g. ^r1 r2 means commits reachable from r2 but exclude the ones reachable from r1 (i.e. r1 and its ancestors).
Dotted Range Notations
The .. (two-dot) Range Notation
The ^r1 r2 set operation appears so often that there is a shorthand for it. When you have two commits r1 and r2 (named according to the syntax explained in SPECIFYING REVISIONS above), you can ask for commits that are reachable from r2 excluding those that are reachable from r1 by ^r1 r2 and it can be written as r1..r2.
The … (three dot) Symmetric Difference Notation
A similar notation r1...r2 is called symmetric difference of r1 and r2 and is defined as r1 r2 --not $(git merge-base --all r1 r2). It is the set of commits that are reachable from either one of r1 (left side) or r2 (right side) but not from both.
In these two shorthand notations, you can omit one end and let it default to HEAD.
For example, origin.. is a shorthand for origin..HEAD and asks "What did I do
since I forked from the origin branch?" Similarly, ..origin is a shorthand for
HEAD..origin and asks "What did the origin do since I forked from them?" Note that
.. would mean HEAD..HEAD which is an empty range that is both reachable and
unreachable from HEAD.
Other <rev>^ Parent Shorthand Notations
Three other shorthands exist, particularly useful for merge commits, for naming a set that is formed by a commit and its parent commits.
The r1^@ notation means all parents of r1.
The r1^! notation includes commit r1 but excludes all of its parents. By itself, this notation denotes the single commit r1.
The <rev>^-<n> notation includes <rev> but excludes the <n>th parent (i.e. a shorthand for <rev>^<n>..<rev>), with <n> = 1 if not given. This is typically useful for merge commits where you can just pass <commit>^- to get all the commits in the branch that was merged in merge commit <commit> (including <commit> itself).
While <rev>^<n> was about specifying a single commit parent, these three notations also consider its parents. For example you can say HEAD^2^@, however you cannot say HEAD^@^2.