}
 
 __git_mergetools_common="diffuse ecmerge emerge kdiff3 meld opendiff
-                       tkdiff vimdiff gvimdiff xxdiff araxis
+                       tkdiff vimdiff gvimdiff xxdiff araxis p4merge
 "
 
 _git_difftool ()
 {
+       __git_has_doubledash && return
+
        local cur="${COMP_WORDS[COMP_CWORD]}"
        case "$cur" in
        --tool=*)
                return
                ;;
        --*)
-               __gitcomp "--tool="
+               __gitcomp "--cached --staged --pickaxe-all --pickaxe-regex
+                       --base --ours --theirs
+                       --no-renames --diff-filter= --find-copies-harder
+                       --relative --ignore-submodules
+                       --tool="
                return
                ;;
        esac
-       COMPREPLY=()
+       __git_complete_file
 }
 
 __git_fetch_options="
                return
                ;;
        esac
-       COMPREPLY=()
+
+       __gitcomp "$(__git_refs)"
 }
 
 _git_help ()
 
 __git_merge_options="
        --no-commit --no-stat --log --no-log --squash --strategy
-       --commit --stat --no-squash --ff --no-ff
+       --commit --stat --no-squash --ff --no-ff --ff-only
 "
 
 _git_merge ()
        fi
        __git_complete_strategy && return
        case "$cur" in
+       --whitespace=*)
+               __gitcomp "$__git_whitespacelist" "" "${cur##--whitespace=}"
+               return
+               ;;
        --*)
-               __gitcomp "--onto --merge --strategy --interactive"
+               __gitcomp "
+                       --onto --merge --strategy --interactive
+                       --preserve-merges --stat --no-stat
+                       --committer-date-is-author-date --ignore-date
+                       --ignore-whitespace --whitespace=
+                       "
+
                return
        esac
        __gitcomp "$(__git_refs)"