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+git-patch-id(1)
+===============
+
+NAME
+----
+git-patch-id - Compute unique ID for a patch
+
+SYNOPSIS
+--------
+[verse]
+'git patch-id' < <patch>
+
+DESCRIPTION
+-----------
+A "patch ID" is nothing but a SHA1 of the diff associated with a patch, with
+whitespace and line numbers ignored.  As such, it's "reasonably stable", but at
+the same time also reasonably unique, i.e., two patches that have the same "patch
+ID" are almost guaranteed to be the same thing.
+
+IOW, you can use this thing to look for likely duplicate commits.
+
+When dealing with 'git diff-tree' output, it takes advantage of
+the fact that the patch is prefixed with the object name of the
+commit, and outputs two 40-byte hexadecimal strings.  The first
+string is the patch ID, and the second string is the commit ID.
+This can be used to make a mapping from patch ID to commit ID.
+
+OPTIONS
+-------
+<patch>::
+	The diff to create the ID of.
+
+GIT
+---
+Part of the linkgit:git[1] suite