templatefuncs: add mailmap template function This commit adds a template function to support the .mailmap file in Mercurial repositories. The .mailmap file comes from git, and can be used to map new emails and names for old commits. The general use case is that someone may change their name or author commits under different emails and aliases, which would make these commits appear as though they came from different persons. The file allows you to specify the correct name that should be used in place of the author field specified in the commit. The mailmap file has 4 possible formats used to map old "commit" names to new "proper" names: 1. <proper@email.com> <commit@email.com> 2. Proper Name <commit@email.com> 3. Proper Name <proper@email.com> <commit@email.com> 4. Proper Name <proper@email.com> Commit Name <commit@email.com> Essentially there is a commit email present in each mailmap entry, that maps to either an updated name, email, or both. The final possible format allows commits authored by a person who used both an old name and an old email to map to a new name and email. To parse the file, we split by spaces and build a name out of every element that does not start with "<". Once we find an element that does start with "<" we concatenate all the name elements that preceded and add that as a parsed name. We then add the email as the first parsed email. We repeat the process until the end of the line, or a comment is found. We will be left with all parsed names in a list, and all parsed emails in a list, with the 0 index being the proper values and the 1 index being the commit values (if they were specified in the entry). The commit values are added as the keys to a dict, and with the proper fields as the values. The mapname function takes the mapping object and the commit author field and attempts to look for a corresponding entry. To do so we try (commit name, commit email) first, and if no results are returned then (None, commit email) is also looked up. This is due to format 4 from above, where someone may have a mailmap entry with both name and email, and if they don't it is possible they have an entry that uses only the commit email. Differential Revision: https://phab.mercurial-scm.org/D2904