====== Updating the .mailmap file ======

The **[[https://git-scm.com/docs/git-check-mailmap#_mapping_authors|.mailmap file]]** allows Git to handle user aliases.

It is useful to maintain a clean and consistent list of authors, for example if users changed e-mail addresses or used different names when checking in their commits.


===== Identifying duplicate authors in Git history =====

This section provides command to identify duplicates that would require an entry in the .mailmap file. 

If there is no output, then there's nothing to do ! :-)

==== Multiple e-mail addresses ====

The following command will print a list of **Author names** having more than one e-mail address not already aliased in mailmap.

<code=bash>
git log --format='%aN <%aE>' | sort -u | awk -F'<' '{print $1}' | uniq -c | grep -v '^ *1 '| cut -c9-
</code>

==== Multiple names ====

The following command will print a list of Author **e-mail addresses** linked to more than one name, and not already aliased in mailmap.

<code=bash>
git log --format='%aE %aN' | sort -u | awk '{print $1}' | uniq -c | grep -v '^ *1 ' | cut -c9-
</code>

===== Updating .mailmap =====

Add aliases to the .mailmap file for each entry in the lists generated by the above commands. The following command will identify what needs to be added (replace ''XXX'' by the entry)

<code>
git log --author="XXX" --format="%aN <%aE>" | sort -u
</code>

See [[#references|Reference section]] below for details about .mailmap file syntax.

===== Example =====

The example below was generated on the MantisBT repository, after removing Victor's aliases from the ''.mailmap'' file.

  - Identify duplicates <code>
$ git log --format='%aN <%aE>' | sort -u | awk -F'<' '{print $1}' | uniq -c | grep -v '^ *1 '| cut -c9-
Victor Boctor 

$ git log --author="Victor Boctor" --format="%aN <%aE>" |sort -u
Victor Boctor <vboctor@gmail.com>
Victor Boctor <vboctor@localhost.localdomain>
Victor Boctor <vboctor@new-host-3.home>
Victor Boctor <victor@mantishub.com>
Victor Boctor <victor@mantishub.net>
</code>
  - Edit ''.mailmap'' file to add aliases <code>
Victor Boctor <vboctor@gmail.com> root <root@localhost.localdomain>
Victor Boctor <vboctor@gmail.com> <vboctor@localhost.localdomain>
Victor Boctor <vboctor@gmail.com> <vboctor@new-host-3.home>
Victor Boctor <vboctor@gmail.com> <victor@mantishub.com>
Victor Boctor <vboctor@gmail.com> <victor@mantishub.net>
</code>
  - Check again: only a single entry is displayed now <code>
$ git log --author="Victor Boctor" --format="%aN <%aE>" |sort -u
Victor Boctor <vboctor@gmail.com>
</code>

===== References =====

  * [[https://git-scm.com/docs/gitmailmap|Git manual]]
  * [[https://blog.developer.atlassian.com/aliasing-authors-in-git/|Aliasing authors in Git (Atlassian blog)]]