git diff, logのドット2つとドット3つ
This is synonymous to the earlier form (without the ..) for viewing the changes between two arbitrary <commit>. If <commit> on one side is omitted, it will have the same effect as using HEAD instead.
This form is to view the changes on the branch containing and up to the second <commit>, starting at a common ancestor of both <commit>. git diff A...B is equivalent to git diff $(git merge-base A B) B. You can omit any one of <commit>, which has the same effect as using HEAD instead.
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