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[PATCH] read-tree: save more user hassles during fast-forward.

This implements the "never lose the current cache information or
the work tree state, but favor a successful merge over merge
failure" principle in the fast-forward two-tree merge operation.

It comes with a set of tests to cover all the cases described in
the case matrix found in the new documentation.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Junio C Hamano 2005-06-07 11:36:30 -07:00 committed by Linus Torvalds
parent 63aff4fed9
commit c859600954
4 changed files with 698 additions and 13 deletions

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@ -53,6 +53,80 @@ the stuff that really changed.
This is used to avoid unnecessary false hits when "git-diff-files" is
run after git-read-tree.
Two Tree Merge
~~~~~~~~~~~~~~
Typically, this is invoked as "git-read-tree -m $H $M", where $H
is the head commit of the current repository, and $M is the head
of a foreign tree, which is simply ahead of $H (i.e. we are in a
fast forward situation).
When two trees are specified, the user is telling git-read-tree
the following:
(1) The current index and work tree is derived from $H, but
the user may have local changes in them since $H;
(2) The user wants to fast-forward to $M.
In this case, the "git-read-tree -m $H $M" command makes sure
that no local change is lost as the result of this "merge".
Here are the "carry forward" rules:
I (index) H M Result
-------------------------------------------------------
0 nothing nothing nothing (does not happen)
1 nothing nothing exists use M
2 nothing exists nothing remove path from cache
3 nothing exists exists use M
clean I==H I==M
------------------
4 yes N/A N/A nothing nothing keep index
5 no N/A N/A nothing nothing keep index
6 yes N/A yes nothing exists keep index
7 no N/A yes nothing exists keep index
8 yes N/A no nothing exists fail
9 no N/A no nothing exists fail
10 yes yes N/A exists nothing remove path from cache
11 no yes N/A exists nothing fail
12 yes no N/A exists nothing fail
13 no no N/A exists nothing fail
clean (H=M)
------
14 yes exists exists keep index
15 no exists exists keep index
clean I==H I==M (H!=M)
------------------
16 yes no no exists exists fail
17 no no no exists exists fail
18 yes no yes exists exists keep index
19 no no yes exists exists keep index
20 yes yes no exists exists use M
21 no yes no exists exists fail
In all "keep index" cases, the cache entry stays as in the
original index file. If the entry were not up to date,
git-read-tree keeps the copy in the work tree intact when
operating under the -u flag.
When this form of git-read-tree returns successfully, you can
see what "local changes" you made are carried forward by running
"git-diff-cache --cached $M". Note that this does not
necessarily match "git-diff-cache --cached $H" would have
produced before such a two tree merge. This is because of cases
18 and 19 --- if you already had the changes in $M (e.g. maybe
you picked it up via e-mail in a patch form), "git-diff-cache
--cached $H" would have told you about the change before this
merge, but it would not show in "git-diff-cache --cached $M"
output after two-tree merge.
3-Way Merge
~~~~~~~~~~~
Each "index" entry has two bits worth of "stage" state. stage 0 is the

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@ -155,28 +155,51 @@ static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **ds
/*
* Two-way merge.
*
* The rule is:
* - every current entry has to match the old tree
* - if the current entry matches the new tree, we leave it
* as-is. Otherwise we require that it be up-to-date.
* The rule is to "carry forward" what is in the index without losing
* information across a "fast forward", favoring a successful merge
* over a merge failure when it makes sense. For details of the
* "carry forward" rule, please see <Documentation/git-read-tree.txt>.
*
*/
static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
{
struct cache_entry *old = src[0];
struct cache_entry *a = src[1], *b = src[2];
struct cache_entry *current = src[0];
struct cache_entry *oldtree = src[1], *newtree = src[2];
if (src[3])
return -1;
if (old) {
if (!a || !same(old, a))
if (current) {
if ((!oldtree && !newtree) || /* 4 and 5 */
(!oldtree && newtree &&
same(current, newtree)) || /* 6 and 7 */
(oldtree && newtree &&
same(oldtree, newtree)) || /* 14 and 15 */
(oldtree && newtree &&
!same(oldtree, newtree) && /* 18 and 19*/
same(current, newtree))) {
*dst++ = current;
return 1;
}
else if (oldtree && !newtree && same(current, oldtree)) {
/* 10 or 11 */
verify_uptodate(current);
return 0;
}
else if (oldtree && newtree &&
same(current, oldtree) && !same(current, newtree)) {
/* 20 or 21 */
verify_uptodate(current);
return merged_entry(newtree, NULL, dst);
}
else
/* all other failures */
return -1;
}
if (b)
return merged_entry(b, old, dst);
if (old)
verify_uptodate(old);
return 0;
else if (newtree)
return merged_entry(newtree, NULL, dst);
else
return 0;
}
/*

281
t/t1001-read-tree-m-2way.sh Executable file
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@ -0,0 +1,281 @@
#!/bin/sh
#
# Copyright (c) 2005 Junio C Hamano
#
test_description='Two way merge with read-tree -m $H $M
This test tries two-way merge (aka fast forward with carry forward).
There is the head (called H) and another commit (called M), which is
simply ahead of H. The index and the work tree contains a state that
is derived from H, but may also have local changes. This test checks
all the combinations described in the two-tree merge "carry forward"
rules, found in <Documentation/git-rev-tree.txt>.
In the test, these paths are used:
bozbar - in H, stays in M, modified from bozbar to gnusto
frotz - not in H added in M
nitfol - in H, stays in M unmodified
rezrov - in H, deleted in M
yomin - not in H nor M
'
. ./test-lib.sh
_x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
_x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
compare_change () {
sed >current \
-e '/^--- /d; /^+++ /d; /^@@ /d;' \
-e 's/^\(.[0-7][0-7][0-7][0-7][0-7][0-7]\) '"$_x40"' /\1 X /' "$1"
diff -u expected current
}
check_cache_at () {
clean_if_empty=`git-diff-files "$1"`
case "$clean_if_empty" in
'') echo "$1: clean" ;;
?*) echo "$1: dirty" ;;
esac
case "$2,$clean_if_empty" in
clean,) : ;;
clean,?*) false ;;
dirty,) false ;;
dirty,?*) : ;;
esac
}
test_expect_success \
setup \
'echo frotz >frotz &&
echo nitfol >nitfol &&
echo bozbar >bozbar &&
echo rezrov >rezrov &&
echo yomin >yomin &&
git-update-cache --add nitfol bozbar rezrov &&
treeH=`git-write-tree` &&
echo treeH $treeH &&
git-ls-tree $treeH &&
echo gnusto >bozbar &&
git-update-cache --add frotz bozbar --force-remove rezrov &&
git-ls-files --stage >M.out &&
treeM=`git-write-tree` &&
echo treeM $treeM &&
git-ls-tree $treeM &&
git-diff-tree $treeH $treeM'
test_expect_success \
'1, 2, 3 - no carry forward' \
'rm -f .git/index &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >1-3.out &&
cmp M.out 1-3.out &&
check_cache_at bozbar dirty &&
check_cache_at frotz dirty &&
check_cache_at nitfol dirty'
echo '+100644 X 0 yomin' >expected
test_expect_success \
'4 - carry forward local addition.' \
'rm -f .git/index &&
git-update-cache --add yomin &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >4.out || exit
diff --unified=0 M.out 4.out >4diff.out
compare_change 4diff.out expected &&
check_cache_at yomin clean'
test_expect_success \
'5 - carry forward local addition.' \
'rm -f .git/index &&
echo yomin >yomin &&
git-update-cache --add yomin &&
echo yomin yomin >yomin &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >5.out || exit
diff --unified=0 M.out 5.out >5diff.out
compare_change 5diff.out expected &&
check_cache_at yomin dirty'
test_expect_success \
'6 - local addition already has the same.' \
'rm -f .git/index &&
git-update-cache --add frotz &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >6.out &&
diff --unified=0 M.out 6.out &&
check_cache_at frotz clean'
test_expect_success \
'7 - local addition already has the same.' \
'rm -f .git/index &&
echo frotz >frotz &&
git-update-cache --add frotz &&
echo frotz frotz >frotz &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >7.out &&
diff --unified=0 M.out 7.out &&
check_cache_at frotz dirty'
test_expect_success \
'8 - conflicting addition.' \
'rm -f .git/index &&
echo frotz frotz >frotz &&
git-update-cache --add frotz &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'9 - conflicting addition.' \
'rm -f .git/index &&
echo frotz frotz >frotz &&
git-update-cache --add frotz &&
echo frotz >frotz &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'10 - path removed.' \
'rm -f .git/index &&
echo rezrov >rezrov &&
git-update-cache --add rezrov &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >10.out &&
cmp M.out 10.out'
test_expect_success \
'11 - dirty path removed.' \
'rm -f .git/index &&
echo rezrov >rezrov &&
git-update-cache --add rezrov &&
echo rezrov rezrov >rezrov &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'12 - unmatching local changes being removed.' \
'rm -f .git/index &&
echo rezrov rezrov >rezrov &&
git-update-cache --add rezrov &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'13 - unmatching local changes being removed.' \
'rm -f .git/index &&
echo rezrov rezrov >rezrov &&
git-update-cache --add rezrov &&
echo rezrov >rezrov &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
cat >expected <<EOF
-100644 X 0 nitfol
+100644 X 0 nitfol
EOF
test_expect_success \
'14 - unchanged in two heads.' \
'rm -f .git/index &&
echo nitfol nitfol >nitfol &&
git-update-cache --add nitfol &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >14.out || exit
diff --unified=0 M.out 14.out >14diff.out
compare_change 14diff.out expected &&
check_cache_at nitfol clean'
test_expect_success \
'15 - unchanged in two heads.' \
'rm -f .git/index &&
echo nitfol nitfol >nitfol &&
git-update-cache --add nitfol &&
echo nitfol nitfol nitfol >nitfol &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >15.out || exit
diff --unified=0 M.out 15.out >15diff.out
compare_change 15diff.out expected &&
check_cache_at nitfol dirty'
test_expect_success \
'16 - conflicting local change.' \
'rm -f .git/index &&
echo bozbar bozbar >bozbar &&
git-update-cache --add bozbar &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'17 - conflicting local change.' \
'rm -f .git/index &&
echo bozbar bozbar >bozbar &&
git-update-cache --add bozbar &&
echo bozbar bozbar bozbar >bozbar &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
test_expect_success \
'18 - local change already having a good result.' \
'rm -f .git/index &&
echo gnusto >bozbar &&
git-update-cache --add bozbar &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >18.out &&
diff --unified=0 M.out 18.out &&
check_cache_at bozbar clean'
test_expect_success \
'19 - local change already having a good result, further modified.' \
'rm -f .git/index &&
echo gnusto >bozbar &&
git-update-cache --add bozbar &&
echo gnusto gnusto >bozbar &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >19.out &&
diff --unified=0 M.out 19.out &&
check_cache_at bozbar dirty'
test_expect_success \
'20 - no local change, use new tree.' \
'rm -f .git/index &&
echo bozbar >bozbar &&
git-update-cache --add bozbar &&
git-read-tree -m $treeH $treeM &&
git-ls-files --stage >20.out &&
diff --unified=0 M.out 20.out &&
check_cache_at bozbar dirty'
test_expect_success \
'21 - no local change, dirty cache.' \
'rm -f .git/index &&
echo bozbar >bozbar &&
git-update-cache --add bozbar &&
echo gnusto gnusto >bozbar &&
if git-read-tree -m $treeH $treeM; then false; else :; fi'
# Also make sure we did not break DF vs DF/DF case.
test_expect_success \
'DF vs DF/DF case setup.' \
'rm -f .git/index &&
echo DF >DF &&
git-update-cache --add DF &&
treeDF=`git-write-tree` &&
echo treeDF $treeDF &&
git-ls-tree $treeDF &&
rm -f DF &&
mkdir DF &&
echo DF/DF >DF/DF &&
git-update-cache --add --remove DF DF/DF &&
treeDFDF=`git-write-tree` &&
echo treeDFDF $treeDFDF &&
git-ls-tree $treeDFDF &&
git-ls-files --stage >DFDF.out'
test_expect_success \
'DF vs DF/DF case test.' \
'rm -f .git/index &&
rm -fr DF &&
echo DF >DF &&
git-update-cache --add DF &&
git-read-tree -m $treeDF $treeDFDF &&
git-ls-files --stage >DFDFcheck.out &&
diff --unified=0 DFDF.out DFDFcheck.out &&
check_cache_at DF/DF dirty'
test_done

307
t/t1002-read-tree-m-u-2way.sh Executable file
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@ -0,0 +1,307 @@
#!/bin/sh
#
# Copyright (c) 2005 Junio C Hamano
#
test_description='Two way merge with read-tree -m -u $H $M
This is identical to t1001, but uses -u to update the work tree as well.
'
. ./test-lib.sh
_x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
_x40="$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40"
compare_change () {
sed >current \
-e '/^--- /d; /^+++ /d; /^@@ /d;' \
-e 's/^\(.[0-7][0-7][0-7][0-7][0-7][0-7]\) '"$_x40"' /\1 X /' "$1"
diff -u expected current
}
check_cache_at () {
clean_if_empty=`git-diff-files "$1"`
case "$clean_if_empty" in
'') echo "$1: clean" ;;
?*) echo "$1: dirty" ;;
esac
case "$2,$clean_if_empty" in
clean,) : ;;
clean,?*) false ;;
dirty,) false ;;
dirty,?*) : ;;
esac
}
test_expect_success \
setup \
'echo frotz >frotz &&
echo nitfol >nitfol &&
echo bozbar >bozbar &&
echo rezrov >rezrov &&
echo yomin >yomin &&
git-update-cache --add nitfol bozbar rezrov &&
treeH=`git-write-tree` &&
echo treeH $treeH &&
git-ls-tree $treeH &&
echo gnusto >bozbar &&
git-update-cache --add frotz bozbar --force-remove rezrov &&
git-ls-files --stage >M.out &&
treeM=`git-write-tree` &&
echo treeM $treeM &&
git-ls-tree $treeM &&
sha1sum bozbar frotz nitfol >M.sha1 &&
git-diff-tree $treeH $treeM'
test_expect_success \
'1, 2, 3 - no carry forward' \
'rm -f .git/index &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >1-3.out &&
cmp M.out 1-3.out &&
sha1sum -c M.sha1 &&
check_cache_at bozbar clean &&
check_cache_at frotz clean &&
check_cache_at nitfol clean'
echo '+100644 X 0 yomin' >expected
test_expect_success \
'4 - carry forward local addition.' \
'rm -f .git/index &&
git-update-cache --add yomin &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >4.out || exit
diff --unified=0 M.out 4.out >4diff.out
compare_change 4diff.out expected &&
check_cache_at yomin clean &&
sha1sum -c M.sha1 &&
echo yomin >yomin1 &&
diff yomin yomin1 &&
rm -f yomin1'
test_expect_success \
'5 - carry forward local addition.' \
'rm -f .git/index &&
echo yomin >yomin &&
git-update-cache --add yomin &&
echo yomin yomin >yomin &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >5.out || exit
diff --unified=0 M.out 5.out >5diff.out
compare_change 5diff.out expected &&
check_cache_at yomin dirty &&
sha1sum -c M.sha1 &&
: dirty index should have prevented -u from checking it out.
echo yomin yomin >yomin1 &&
diff yomin yomin1 &&
rm -f yomin1'
test_expect_success \
'6 - local addition already has the same.' \
'rm -f .git/index &&
git-update-cache --add frotz &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >6.out &&
diff --unified=0 M.out 6.out &&
check_cache_at frotz clean &&
sha1sum -c M.sha1 &&
echo frotz >frotz1 &&
diff frotz frotz1 &&
rm -f frotz1'
test_expect_success \
'7 - local addition already has the same.' \
'rm -f .git/index &&
echo frotz >frotz &&
git-update-cache --add frotz &&
echo frotz frotz >frotz &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >7.out &&
diff --unified=0 M.out 7.out &&
check_cache_at frotz dirty &&
if sha1sum -c M.sha1; then false; else :; fi &&
: dirty index should have prevented -u from checking it out.
echo frotz frotz >frotz1 &&
diff frotz frotz1 &&
rm -f frotz1'
test_expect_success \
'8 - conflicting addition.' \
'rm -f .git/index &&
echo frotz frotz >frotz &&
git-update-cache --add frotz &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'9 - conflicting addition.' \
'rm -f .git/index &&
echo frotz frotz >frotz &&
git-update-cache --add frotz &&
echo frotz >frotz &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'10 - path removed.' \
'rm -f .git/index &&
echo rezrov >rezrov &&
git-update-cache --add rezrov &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >10.out &&
cmp M.out 10.out &&
sha1sum -c M.sha1'
test_expect_success \
'11 - dirty path removed.' \
'rm -f .git/index &&
echo rezrov >rezrov &&
git-update-cache --add rezrov &&
echo rezrov rezrov >rezrov &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'12 - unmatching local changes being removed.' \
'rm -f .git/index &&
echo rezrov rezrov >rezrov &&
git-update-cache --add rezrov &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'13 - unmatching local changes being removed.' \
'rm -f .git/index &&
echo rezrov rezrov >rezrov &&
git-update-cache --add rezrov &&
echo rezrov >rezrov &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
cat >expected <<EOF
-100644 X 0 nitfol
+100644 X 0 nitfol
EOF
test_expect_success \
'14 - unchanged in two heads.' \
'rm -f .git/index &&
echo nitfol nitfol >nitfol &&
git-update-cache --add nitfol &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >14.out || exit
diff --unified=0 M.out 14.out >14diff.out
compare_change 14diff.out expected &&
check_cache_at nitfol clean &&
grep -v nitfol M.sha1 | sha1sum -c &&
if sha1sum -c M.sha1; then false; else :; fi &&
echo nitfol nitfol >nitfol1 &&
diff nitfol nitfol1 &&
rm -f nitfol1'
test_expect_success \
'15 - unchanged in two heads.' \
'rm -f .git/index &&
echo nitfol nitfol >nitfol &&
git-update-cache --add nitfol &&
echo nitfol nitfol nitfol >nitfol &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >15.out || exit
diff --unified=0 M.out 15.out >15diff.out
compare_change 15diff.out expected &&
check_cache_at nitfol dirty &&
grep -v nitfol M.sha1 | sha1sum -c &&
if sha1sum -c M.sha1; then false; else :; fi &&
echo nitfol nitfol nitfol >nitfol1 &&
diff nitfol nitfol1 &&
rm -f nitfol1'
test_expect_success \
'16 - conflicting local change.' \
'rm -f .git/index &&
echo bozbar bozbar >bozbar &&
git-update-cache --add bozbar &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'17 - conflicting local change.' \
'rm -f .git/index &&
echo bozbar bozbar >bozbar &&
git-update-cache --add bozbar &&
echo bozbar bozbar bozbar >bozbar &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
test_expect_success \
'18 - local change already having a good result.' \
'rm -f .git/index &&
echo gnusto >bozbar &&
git-update-cache --add bozbar &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >18.out &&
diff --unified=0 M.out 18.out &&
check_cache_at bozbar clean &&
sha1sum -c M.sha1'
test_expect_success \
'19 - local change already having a good result, further modified.' \
'rm -f .git/index &&
echo gnusto >bozbar &&
git-update-cache --add bozbar &&
echo gnusto gnusto >bozbar &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >19.out &&
diff --unified=0 M.out 19.out &&
check_cache_at bozbar dirty &&
grep -v bozbar M.sha1 | sha1sum -c &&
if sha1sum -c M.sha1; then false; else :; fi &&
echo gnusto gnusto >bozbar1 &&
diff bozbar bozbar1 &&
rm -f bozbar1'
test_expect_success \
'20 - no local change, use new tree.' \
'rm -f .git/index &&
echo bozbar >bozbar &&
git-update-cache --add bozbar &&
git-read-tree -m -u $treeH $treeM &&
git-ls-files --stage >20.out &&
diff --unified=0 M.out 20.out &&
check_cache_at bozbar clean &&
sha1sum -c M.sha1'
test_expect_success \
'21 - no local change, dirty cache.' \
'rm -f .git/index &&
echo bozbar >bozbar &&
git-update-cache --add bozbar &&
echo gnusto gnusto >bozbar &&
if git-read-tree -m -u $treeH $treeM; then false; else :; fi'
# Also make sure we did not break DF vs DF/DF case.
test_expect_success \
'DF vs DF/DF case setup.' \
'rm -f .git/index &&
echo DF >DF &&
git-update-cache --add DF &&
treeDF=`git-write-tree` &&
echo treeDF $treeDF &&
git-ls-tree $treeDF &&
rm -f DF &&
mkdir DF &&
echo DF/DF >DF/DF &&
git-update-cache --add --remove DF DF/DF &&
treeDFDF=`git-write-tree` &&
echo treeDFDF $treeDFDF &&
git-ls-tree $treeDFDF &&
git-ls-files --stage >DFDF.out'
test_expect_success \
'DF vs DF/DF case test.' \
'rm -f .git/index &&
rm -fr DF &&
echo DF >DF &&
git-update-cache --add DF &&
git-read-tree -m -u $treeDF $treeDFDF &&
git-ls-files --stage >DFDFcheck.out &&
diff --unified=0 DFDF.out DFDFcheck.out &&
check_cache_at DF/DF clean'
test_done