mailmap doc: create a new "gitmailmap(5)" man page

Create a gitmailmap(5) page similar to how .gitmodules and .gitignore
have their own pages at gitmodules(5) and gitignore(5). Now instead of
"check-mailmap", "blame" and "shortlog" documentation including the
description of the format we link to one canonical place.

This makes things easier for readers, since in our manpage or
web-based[1] output it's not clear that the "MAPPING AUTHORS" sections
aren't subtly different, as opposed to just included.

1. https://git-scm.com/docs/git-check-mailmap

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/Makefile

@@ -21,6 +21,7 @@ MAN1_TXT += gitweb.txt
 MAN5_TXT += gitattributes.txt
 MAN5_TXT += githooks.txt
 MAN5_TXT += gitignore.txt
+MAN5_TXT += gitmailmap.txt
 MAN5_TXT += gitmodules.txt
 MAN5_TXT += gitrepository-layout.txt
 MAN5_TXT += gitweb.conf.txt

Documentation/git-blame.txt

@@ -226,7 +226,7 @@ commit commentary), a blame viewer will not care.
 MAPPING AUTHORS
 ---------------
 
-include::mailmap.txt[]
+See linkgit:gitmailmap[5].
 
 
 SEE ALSO

Documentation/git-check-mailmap.txt

@@ -39,7 +39,7 @@ printed; otherwise only ``$$<user@host>$$'' is printed.
 MAPPING AUTHORS
 ---------------
 
-include::mailmap.txt[]
+See linkgit:gitmailmap[5].
 
 
 GIT

Documentation/git-shortlog.txt

@@ -111,11 +111,7 @@ include::rev-list-options.txt[]
 MAPPING AUTHORS
 ---------------
 
-The `.mailmap` feature is used to coalesce together commits by the same
+See linkgit:gitmailmap[5].
-person in the shortlog, where their name and/or email address was
-spelled differently.
-
-include::mailmap.txt[]
 
 GIT
 ---

Documentation/gitmailmap.txt

@@ -1,9 +1,28 @@
+gitmailmap(5)
+=============
+
+NAME
+----
+gitmailmap - Map author/committer names and/or E-Mail addresses
+
+SYNOPSIS
+--------
+$GIT_WORK_DIR/.mailmap
+
+
+DESCRIPTION
+-----------
+
 If the file `.mailmap` exists at the toplevel of the repository, or at
 the location pointed to by the mailmap.file or mailmap.blob
 configuration options, it
 is used to map author and committer names and email addresses to
 canonical real names and email addresses.
 
+
+SYNTAX
+------
+
 In the simple form, each line in the file consists of the canonical
 real name of an author, whitespace, and an email address used in the
 commit (enclosed by '<' and '>') to map to the name. For example:
@@ -27,6 +46,10 @@ commit matching the specified commit email address, and:
 which allows mailmap to replace both the name and the email of a
 commit matching both the specified commit name and email address.
 
+
+EXAMPLES
+--------
+
 Example 1: Your history contains commits by two authors, Jane
 and Joe, whose names appear in the repository under several forms:
 
@@ -73,3 +96,13 @@ Santa Claus <santa.claus@northpole.xx> <me@company.xx>
 
 Use hash '#' for comments that are either on their own line, or after
 the email address.
+
+
+SEE ALSO
+--------
+linkgit:git-check-mailmap[1]
+
+
+GIT
+---
+Part of the linkgit:git[1] suite

command-list.txt

@@ -204,6 +204,7 @@ gitfaq                                  guide
 gitglossary                             guide
 githooks                                guide
 gitignore                               guide
+gitmailmap                              guide
 gitmodules                              guide
 gitnamespaces                           guide
 gitremote-helpers                       guide