git commit ... [--author=<author>]

$ git init
Initialized empty Git repository in c:/projects/bb/.git/

$ touch a
$ git add a
$ git commit -m "new file" --author="Author Name <email@address.com>"
[master (root-commit) cb6ca75] new file
 Author: Author Name <email@address.com>
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 a

$ git log
commit cb6ca75753e13de07202f131d730c68df1a96941
Author: Author Name <email@address.com>
Date:   Thu Aug 13 12:24:21 2015 +0300

    new file

git config --local alias.com 'commit --author="Author Name <email@address.com>"'

$ touch file2
$ git add file2
$ git com -m "File2"
[master ed88a10] File2
 Author: Author Name <email@address.com>
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 file2

$ git log
commit ed88a10d1e1fef95cebd7d9cbc028314e6a3fa54
Author: Author Name <email@address.com>
Date:   Thu Aug 13 12:46:48 2015 +0300

    File2
commit cb6ca75753e13de07202f131d730c68df1a96941
Author: Author Name <email@address.com>
Date:   Thu Aug 13 12:24:21 2015 +0300

    new file