undef/git-commit-vandalism
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filter-branch: fix variable export logic

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filter-branch tries to restore "old" copies of some
environment variables by using the construct:

  unset var
  test -z "$old_var" || var="$old_var" && export var

This is just wrong.  AND-list and OR-list operators && and || have equal
precedence and they bind left to right.  The second term, var="$old"
assignment always succeeds, so we always end up exporting var.

On bash and dash, exporting an unset variable has no effect. However, on
some shells (such as FreeBSD's /bin/sh), the shell exports the empty
value.

This manifested itself in this case as git-filter-branch setting
GIT_INDEX_FILE to the empty string, which in turn caused its call to
git-read-tree to fail, leaving the working tree pointing at the original
HEAD instead of the rewritten one.

To fix this, we change the short-circuit logic to better match the intent:

  test -z "$old_var" || {
    var="$old_var" && export var
  }

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2008-05-13 04:46:38 -04:00 committed by Junio C Hamano
parent 6d9878cc60
commit 0bdf93cbf0
1 changed files with 9 additions and 3 deletions
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12
git-filter-branch.sh
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@ -435,11 +435,17 @@ rm -rf "$tempdir"
trap - 0
unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE
test -z "$ORIG_GIT_DIR" || GIT_DIR="$ORIG_GIT_DIR" && export GIT_DIR
test -z "$ORIG_GIT_WORK_TREE" || GIT_WORK_TREE="$ORIG_GIT_WORK_TREE" &&
test -z "$ORIG_GIT_DIR" || {
GIT_DIR="$ORIG_GIT_DIR" && export GIT_DIR
}
test -z "$ORIG_GIT_WORK_TREE" || {
GIT_WORK_TREE="$ORIG_GIT_WORK_TREE" &&
export GIT_WORK_TREE
test -z "$ORIG_GIT_INDEX_FILE" || GIT_INDEX_FILE="$ORIG_GIT_INDEX_FILE" &&
}
test -z "$ORIG_GIT_INDEX_FILE" || {
GIT_INDEX_FILE="$ORIG_GIT_INDEX_FILE" &&
export GIT_INDEX_FILE
}
git read-tree -u -m HEAD
exit $ret