completion: recognize more long-options

completion: recognize more long-options

Command completion only recognizes a subset of the available options for
the various git commands. The set of recognized options needs to balance
between having all useful options and to not clutter the terminal.

This commit adds all long-options that are mentioned in the man-page
synopsis of the respective git command. Possibly dangerous options are
not included in this set, to avoid accidental data loss. The added
options are:

 - apply: --recount --directory=
 - archive: --output
 - branch: --column --no-column --sort= --points-at
 - clone: --no-single-branch --shallow-submodules
 - commit: --patch --short --date --allow-empty
 - describe: --first-parent
 - fetch, pull: --unshallow --update-shallow
 - fsck: --name-objects
 - grep: --break --heading --show-function --function-context
         --untracked --no-index
 - mergetool: --prompt --no-prompt
 - reset: --keep
 - revert: --strategy= --strategy-option=
 - shortlog: --email
 - tag: --merged --no-merged --create-reflog

Signed-off-by: Cornelius Weig <cornelius.weig@tngtech.com>
Helped-by: Johannes Sixt <j6t@kdbg.org>
Reviewed-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>