outputs code for use with eval to set the GIT_AUTHOR_NAME,
GIT_AUTHOR_EMAIL and GIT_AUTHOR_DATE variables for a given commit.
+create_virtual_base::
+ modifies the first file so only lines in common with the
+ second file remain. If there is insufficient common material,
+ then the first file is left empty. The result is suitable
+ as a virtual base input for a 3-way merge.
+
GIT
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Part of the linkgit:git[1] suite