diff --git a/etc/bash_completion.sh b/etc/bash_completion.sh
index c2be086a3..6d4b3bdda 100644
--- a/etc/bash_completion.sh
+++ b/etc/bash_completion.sh
@@ -26,6 +26,31 @@ _git_authors(){
   __gitcomp "-l --list --no-email"
 }
 
+_git_coauthor(){
+  local oldIfs=$IFS
+  IFS=$'\n'
+  local cur="${COMP_WORDS[COMP_CWORD]}"
+  local selection=
+  if ((COMP_CWORD == 2)); then
+    for line in $(git authors --list); do
+      selection+="${line% *}"$'\n'
+    done
+  elif ((COMP_CWORD == 3)); then
+    local chosen_name="${COMP_WORDS[COMP_CWORD-1]}"
+    for line in $(git authors --list); do
+      if [ "$chosen_name" = "${line% *}" ]; then
+        local email=${line#*<}
+        email=${email%>*}
+        selection+="$email"$'\n'
+      fi
+    done
+  fi
+  compopt +o default
+  compopt -o filenames
+  COMPREPLY=($(compgen -W "$selection" -- "$cur"))
+  IFS=$oldIfs
+}
+
 _git_contrib(){
 # git completion function modified from
 # https://github.com/markgandolfo/git-bash-completion/blob/master/git-completion.bash
diff --git a/etc/git-extras-completion.zsh b/etc/git-extras-completion.zsh
index aa0f881b3..565ffb719 100644
--- a/etc/git-extras-completion.zsh
+++ b/etc/git-extras-completion.zsh
@@ -101,6 +101,33 @@ __gitex_author_names() {
     _wanted author-names expl author-name compadd $* - $author_names
 }
 
+__gitex_author_emails2() {
+    echo "$g s
+    # read -Ac words
+    # read -cn cword
+
+    local expl
+    declare -a author_names=($state)
+
+    local name="${words[2]}" # name of the author supplied on the command line
+    local -a authors=("${(f)$(git authors --list)}")
+    for line in "${authors[@]}"; do
+        if [ "${line% *}" = "$name" ]; then
+            local email=${line#*<}
+            email=${email%>*}
+
+            author_names+=("${email#* }")
+        fi
+    done
+
+    # _wanted author-names expl author-name compadd $* - $author_names
+    reply=(a b c)
+}
+
+__gitex_author_emails() {
+    compctl -K __gitex_author_emails2
+}
+
 # subcommands
 # new subcommand should be added in alphabetical order
 _git-authors() {
@@ -121,9 +148,10 @@ _git-clear() {
 }
 
 _git-coauthor() {
-    _arguments \
-        ':co-author[co-author to add]' \
-        ':co-author-email[email address of co-author to add]'
+    compctl -K __gitex_author_emails2 a
+    # _arguments \
+    #     ':co-author[co-author to add]:__gitex_author_names' \
+    #     ':co-author-email[email address of co-author to add]:__gitex_author_emails'
 }
 
 _git-contrib() {
diff --git a/etc/git-extras.fish b/etc/git-extras.fish
index ac0c5bde1..0a0b49d2e 100644
--- a/etc/git-extras.fish
+++ b/etc/git-extras.fish
@@ -71,20 +71,20 @@ set __fish_git_extras_commands \
     "unlock:Unlock a file excluded from version control"
 
 # completion for git-extras itself
-complete -c git -f -n '__fish_git_needs_command' -a 'extras' -d 'GIT utilities: repo summary, repl, changelog population, and more'
+complete -c git -f -n __fish_git_needs_command -a extras -d 'GIT utilities: repo summary, repl, changelog population, and more'
 complete -c git -f -n '__fish_git_using_command extras' -s h -l help -d 'Show the help message, can be used for any git-extras commands'
 complete -c git -f -n '__fish_git_using_command extras' -s v -l version -d 'Show git-extras version number'
-complete -c git -f -n '__fish_git_using_command extras; and not contains -- update (commandline -opc)' -a "update" -d 'Self update'
+complete -c git -f -n '__fish_git_using_command extras; and not contains -- update (commandline -opc)' -a update -d 'Self update'
 
 # completion for git-extras provided commands
 set __fish_git_extras_commands (printf -- '%s\n' $__fish_git_extras_commands | sed 's/:/\textras:/' | string collect | string escape)
-complete -c git -n '__fish_git_needs_command' -a "$__fish_git_extras_commands"
+complete -c git -n __fish_git_needs_command -a "$__fish_git_extras_commands"
 # authors
 complete -c git -f -n '__fish_git_using_command authors' -s l -l list -d 'show authors'
 complete -c git -f -n '__fish_git_using_command authors' -l no-email -d 'without email'
 # bulk
-complete -c git    -n '__fish_git_using_command bulk' -s a -d 'Run a git command on all workspaces and their repositories'
-complete -c git    -n '__fish_git_using_command bulk' -s g -d 'Ask the user for confirmation on every execution'
+complete -c git -n '__fish_git_using_command bulk' -s a -d 'Run a git command on all workspaces and their repositories'
+complete -c git -n '__fish_git_using_command bulk' -s g -d 'Ask the user for confirmation on every execution'
 complete -c git -x -n '__fish_git_using_command bulk' -s w -d 'Run on specified workspace'
 complete -c git -x -n '__fish_git_using_command bulk' -l addworkspace -d 'Register a workspace for builk operations'
 complete -c git -x -n '__fish_git_using_command bulk; and contains addworkspace (commandline -opc)' -l addworkspace -d 'the URL or file with URLs to be added'
@@ -103,6 +103,31 @@ complete -c git -f -n '__fish_git_using_command changelog' -s n -l no-merges -d
 complete -c git -f -n '__fish_git_using_command changelog' -s m -l merges-only -d 'Uses only merge commits (commits with more than 1 parent) for generated changelog'
 complete -c git -f -n '__fish_git_using_command changelog' -s p -l prune-old -d 'Replace existing changelog entirely with newly generated content'
 complete -c git -f -n '__fish_git_using_command changelog' -s x -l stdout -d 'Write output to stdout instead of to a new changelog file'
+# coauthor
+function __fish_git_arg_number -a number
+    set -l cmd (commandline -opc)
+    test (count $cmd) -eq $number
+end
+function __fish_git_extra_coauthor_name
+    for line in (git authors --list)
+        printf '%s\n' $line | string replace --regex ' <.*' ''
+    end
+end
+function __fish_git_extra_coauthor_email
+    set -l cmd (commandline -opc)
+    # name provided in the previous positional argument
+    set -l name $cmd[3]
+
+    for line in (git authors --list)
+        set -l loop_name (printf '%s\n' $line | string replace --regex ' <.*' '')
+
+        if test "$name" = "$loop_name"
+            printf '%s\n' $line | string replace --regex '.*?<' '' | string replace --regex '>.*?' ''
+        end
+    end
+end
+complete -c git -f -n '__fish_git_using_command coauthor; and __fish_git_arg_number 2' -a '(__fish_git_extra_coauthor_name)'
+complete -c git -f -n '__fish_git_using_command coauthor; and __fish_git_arg_number 3' -a '(__fish_git_extra_coauthor_email)'
 # count
 complete -c git -f -n '__fish_git_using_command count' -l all -d 'detailed commit count'
 # create-branch
@@ -119,18 +144,18 @@ complete -c git -x -n "__fish_git_using_command delete-tag" -a '(__fish_git for-
 complete -c git -f -n '__fish_git_using_command effort' -l above -d 'ignore file with less than x commits'
 # feature
 complete -c git -x -n '__fish_git_using_command feature' -s a -l alias -d 'use branch_prefix instead of feature'
-complete -c git -f -n '__fish_git_using_command feature; and not contains -- finish (commandline -opc)' -a "finish" -d 'merge and delete the feature branch'
+complete -c git -f -n '__fish_git_using_command feature; and not contains -- finish (commandline -opc)' -a finish -d 'merge and delete the feature branch'
 complete -c git -f -n '__fish_git_using_command feature; and contains -- finish (commandline -opc)' -l squash -d 'Run a squash merge'
 complete -c git -x -n '__fish_git_using_command feature; and contains -- finish (commandline -opc)' -a '(__fish_git for-each-ref --format="%(refname)" 2>/dev/null | grep "refs/heads/feature")' -d 'name of feature branch'
 complete -c git -x -n '__fish_git_using_command feature; and not contains -- finish (commandline -opc)' -s r -l remote -a '(__fish_git_unique_remote_branches)' -d 'Setup a remote tracking branch'
 # graft
-complete -c git -x -n '__fish_git_using_command graft' -s r -l remote -a '(__fish_git_branches)' -d 'src-branch-name'
-complete -c git -x -n '__fish_git_using_command graft' -s r -l remote -a '(__fish_git_branches)' -d 'dest-branch-name'
+complete -c git -x -n '__fish_git_using_command graft' -s r -l remote -a '(__fish_git_branches)' -d src-branch-name
+complete -c git -x -n '__fish_git_using_command graft' -s r -l remote -a '(__fish_git_branches)' -d dest-branch-name
 # guilt
 complete -c git -f -n '__fish_git_using_command guilt' -s w -l ignore-whitespace -d 'ignore whitespace only changes'
 complete -c git -f -n '__fish_git_using_command guilt' -s e -l email -d 'display author emails instead of names'
 complete -c git -f -n '__fish_git_using_command guilt' -s d -l debug -d 'output debug information'
-complete -c git -f -n '__fish_git_using_command guilt' -s h          -d 'output usage information'
+complete -c git -f -n '__fish_git_using_command guilt' -s h -d 'output usage information'
 # ignore
 complete -c git -f -n '__fish_git_using_command ignore' -s l -l local -d 'show local gitignore'
 complete -c git -f -n '__fish_git_using_command ignore' -s g -l global -d 'show global gitignore'
@@ -149,7 +174,7 @@ complete -c git -x -n '__fish_git_using_command ignore-io' -s s -l search -d 'se
 complete -c git -x -n '__fish_git_using_command ignore-io' -s t -l show-update-time -d 'Show the last modified time of ~/.gi_list'
 complete -c git -x -n '__fish_git_using_command ignore-io' -s u -l update -d 'Update ~/.gi_list'
 # merge-into
-complete -c git    -n '__fish_git_using_command merge-into' -l ff-only -d 'merge only fast-forward'
+complete -c git -n '__fish_git_using_command merge-into' -l ff-only -d 'merge only fast-forward'
 complete -c git -x -n '__fish_git_using_command merge-into' -a '(__fish_git_branches)'
 # missing
 complete -c git -x -n '__fish_git_using_command missing' -a '(__fish_git_branches)'
@@ -159,23 +184,23 @@ complete -c git -x -n '__fish_git_using_command squash' -l squash-msg -d 'commit
 # stamp
 complete -c git -x -n '__fish_git_using_command stamp' -s r -l replace -d 'replace stamps with same id'
 # standup
-complete -c git -x -n '__fish_git_using_command standup' -s a -d 'Specify the author of commits. Use "all" to specify all authors'
+complete -c git -x -n '__fish_git_using_command standup' -s a -d 'Specify the author of commits. Use all to specify all authors'
 complete -c git -x -n '__fish_git_using_command standup' -s m -d 'The depth of recursive directory search'
 complete -c git -x -n '__fish_git_using_command standup' -s d -d 'Show history since N days ago'
 complete -c git -x -n '__fish_git_using_command standup' -s D -d 'Specify the date format displayed in commit history'
-complete -c git    -n '__fish_git_using_command standup' -s f -d 'Fetch commits before showing history'
-complete -c git    -n '__fish_git_using_command standup' -s g -d 'Display GPG signed info'
-complete -c git    -n '__fish_git_using_command standup' -s h -l help -d 'Display help message'
-complete -c git    -n '__fish_git_using_command standup' -s L -d 'Enable the inclusion of symbolic links'
-complete -c git    -n '__fish_git_using_command standup' -s B -d 'Display the commits in branch group'
+complete -c git -n '__fish_git_using_command standup' -s f -d 'Fetch commits before showing history'
+complete -c git -n '__fish_git_using_command standup' -s g -d 'Display GPG signed info'
+complete -c git -n '__fish_git_using_command standup' -s h -l help -d 'Display help message'
+complete -c git -n '__fish_git_using_command standup' -s L -d 'Enable the inclusion of symbolic links'
+complete -c git -n '__fish_git_using_command standup' -s B -d 'Display the commits in branch group'
 complete -c git -x -n '__fish_git_using_command standup' -s n -d 'Limit the number of commits displayed per group'
 # summary
-complete -c git    -n '__fish_git_using_command summary' -l line -d 'summarize with lines rather than commits'
-complete -c git    -n '__fish_git_using_command summary' -l dedup-by-email -d 'remove duplicate users by the email address'
-complete -c git    -n '__fish_git_using_command summary' -l no-merges -d 'exclude merge commits'
+complete -c git -n '__fish_git_using_command summary' -l line -d 'summarize with lines rather than commits'
+complete -c git -n '__fish_git_using_command summary' -l dedup-by-email -d 'remove duplicate users by the email address'
+complete -c git -n '__fish_git_using_command summary' -l no-merges -d 'exclude merge commits'
 # release
 complete -c git -x -n '__fish_git_using_command release' -s c -d 'Generates/populates the changelog with all commit message since the last tag'
-complete -c git -x -n '__fish_git_using_command release' -s r -d 'The "remote" repository that is destination of a push operation'
+complete -c git -x -n '__fish_git_using_command release' -s r -d 'The remote repository that is destination of a push operation'
 complete -c git -x -n '__fish_git_using_command release' -s m -d 'use the custom commit information instead of the default message'
 complete -c git -x -n '__fish_git_using_command release' -s s -d 'Create a signed and annotated tag'
 complete -c git -x -n '__fish_git_using_command release' -s u -d 'Create a tag, annotated and signed with the given key'
@@ -184,5 +209,3 @@ complete -c git -x -n '__fish_git_using_command release' -l no-empty-commit -d '
 # undo
 complete -c git -x -n '__fish_git_using_command undo' -s s -l soft -d 'only rolls back the commit but changes remain un-staged'
 complete -c git -x -n '__fish_git_using_command undo' -s h -l hard -d 'wipes your commit(s)'
-
-
diff --git a/etc/test.fish b/etc/test.fish
new file mode 100644
index 000000000..159e97d8f
--- /dev/null
+++ b/etc/test.fish
@@ -0,0 +1,20 @@
+complete -e blah
+
+function __fish_git_arg_number -a number
+    set -l cmd (commandline -opc)
+    test (count $cmd) -eq $number
+end
+
+function __fish_git_extra_coauthor_name
+    printf '%s\n' 'a' 'apple' 'ann'
+end
+
+function __fish_git_extra_coauthor_email
+    set -l cmd (commandline -opc)
+
+    set -l value $cmd[3]
+    printf '%s\n' 'n' 'n1' 'n2' "$value"
+end
+
+complete -c blah -f -n '__fish_git_using_command coauthor; and __fish_git_arg_number 2' -a '(__fish_git_extra_coauthor_name)'
+complete -c blah -f -n '__fish_git_using_command coauthor; and __fish_git_arg_number 3' -a '(__fish_git_extra_coauthor_email)'