filter-branch: add `--setup` step

A `--setup` step in `git filter-branch` makes it much easier to
define the initial values of variables used in the real filters.
Also sourcing/defining utility functions here instead of
`--env-filter` improves performance and minimizes clogging the
output in case of errors.

Signed-off-by: Andreas Heiduk <asheiduk@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index 7b695db..9e5169a 100644 (file)
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -8,11 +8,11 @@ git-filter-branch - Rewrite branches
 SYNOPSIS
 --------
 [verse]
-'git filter-branch' [--env-filter <command>] [--tree-filter <command>]
-       [--index-filter <command>] [--parent-filter <command>]
-       [--msg-filter <command>] [--commit-filter <command>]
-       [--tag-name-filter <command>] [--subdirectory-filter <directory>]
-       [--prune-empty]
+'git filter-branch' [--setup <command>] [--env-filter <command>]
+       [--tree-filter <command>] [--index-filter <command>]
+       [--parent-filter <command>] [--msg-filter <command>]
+       [--commit-filter <command>] [--tag-name-filter <command>]
+       [--subdirectory-filter <directory>] [--prune-empty]
        [--original <namespace>] [-d <directory>] [-f | --force]
        [--] [<rev-list options>...]
 
@@ -82,6 +82,13 @@ multiple commits.
 OPTIONS
 -------
 
+--setup <command>::
+       This is not a real filter executed for each commit but a one
+       time setup just before the loop. Therefore no commit-specific
+       variables are defined yet.  Functions or variables defined here
+       can be used or modified in the following filter steps except
+       the commit filter, for technical reasons.
+
 --env-filter <command>::
        This filter may be used if you only need to modify the environment
        in which the commit will be performed.  Specifically, you might

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index aafaf70..2758ae5 100755 (executable)
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -81,11 +81,12 @@ set_ident () {
        finish_ident COMMITTER
 }
 
-USAGE="[--env-filter <command>] [--tree-filter <command>]
-       [--index-filter <command>] [--parent-filter <command>]
-       [--msg-filter <command>] [--commit-filter <command>]
-       [--tag-name-filter <command>] [--subdirectory-filter <directory>]
-       [--original <namespace>] [-d <directory>] [-f | --force]
+USAGE="[--setup <command>] [--env-filter <command>]
+       [--tree-filter <command>] [--index-filter <command>]
+       [--parent-filter <command>] [--msg-filter <command>]
+       [--commit-filter <command>] [--tag-name-filter <command>]
+       [--subdirectory-filter <directory>] [--original <namespace>]
+       [-d <directory>] [-f | --force]
        [<rev-list options>...]"
 
 OPTIONS_SPEC=
@@ -96,6 +97,7 @@ if [ "$(is_bare_repository)" = false ]; then
 fi
 
 tempdir=.git-rewrite
+filter_setup=
 filter_env=
 filter_tree=
 filter_index=
@@ -148,6 +150,9 @@ do
        -d)
                tempdir="$OPTARG"
                ;;
+       --setup)
+               filter_setup="$OPTARG"
+               ;;
        --env-filter)
                filter_env="$OPTARG"
                ;;
@@ -317,6 +322,9 @@ else
        need_index=
 fi
 
+eval "$filter_setup" < /dev/null ||
+       die "filter setup failed: $filter_setup"
+
 while read commit parents; do
        git_filter_branch__commit_count=$(($git_filter_branch__commit_count+1))