bash completion: Improve responsiveness of git-log completion

Junio noticed the bash completion has been taking a long time lately.
Petr Baudis tracked it down to 72e5e989b ("bash: Add space after
unique command name is completed.").  Tracing the code showed
we spent significant time inside of this loop within __gitcomp,
due to the string copying overhead.

  [28.146109654] _git common over
  [28.164791148] gitrefs in
  [28.280302268] gitrefs dir out
  [28.300939737] gitcomp in
  [28.308378112] gitcomp pre-case
* [28.313407453] gitcomp iter in
* [28.701270296] gitcomp iter out
  [28.713370786] out normal

Since __git_refs avoids this string copying by forking and using
echo we use the same trick here when we need to finish generating
the names for the caller.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index cff28a88afe3262705acc3d9b47e97be65dbb8d1..0734ea313c0f0103ad339ab49229636d49d5e99d 100755 (executable)
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -114,9 +114,20 @@ __git_ps1 ()
        fi
 }
 
+__gitcomp_1 ()
+{
+       local c IFS=' '$'\t'$'\n'
+       for c in $1; do
+               case "$c$2" in
+               --*=*) printf %s$'\n' "$c$2" ;;
+               *.)    printf %s$'\n' "$c$2" ;;
+               *)     printf %s$'\n' "$c$2 " ;;
+               esac
+       done
+}
+
 __gitcomp ()
 {
-       local all c s=$'\n' IFS=' '$'\t'$'\n'
        local cur="${COMP_WORDS[COMP_CWORD]}"
        if [ $# -gt 2 ]; then
                cur="$3"
@@ -124,21 +135,14 @@ __gitcomp ()
        case "$cur" in
        --*=)
                COMPREPLY=()
-               return
                ;;
        *)
-               for c in $1; do
-                       case "$c$4" in
-                       --*=*) all="$all$c$4$s" ;;
-                       *.)    all="$all$c$4$s" ;;
-                       *)     all="$all$c$4 $s" ;;
-                       esac
-               done
+               local IFS=$'\n'
+               COMPREPLY=($(compgen -P "$2" \
+                       -W "$(__gitcomp_1 "$1" "$4")" \
+                       -- "$cur"))
                ;;
        esac
-       IFS=$s
-       COMPREPLY=($(compgen -P "$2" -W "$all" -- "$cur"))
-       return
 }
 
 __git_heads ()