tests: allow user to specify trash directory location

The tests generate a large amount of I/O activity creating
and destroying repositories and files. We can improve the
time it takes to run the test suite by creating trash
directories on filesystems with better performance
characteristic, even though we may not want the rest of the
git repository on those filesystems (e.g., because they are
not network connected, or because they are temporary
ramdisks).

For example, on a dual processor system:

$ cd t && time make -j32
real    1m51.562s
user    0m59.260s
sys     1m20.933s

# /dev/shm is tmpfs
$ cd t && time make -j32 GIT_TEST_OPTS="--root=/dev/shm"
real    1m1.484s
user    0m53.555s
sys     1m5.264s

We almost halve the wall clock time, and we utilize the
dual processors much better.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/test-lib.sh b/t/test-lib.sh
index e6a7bb1b45e75b7f28a193364a705e51c7f9a154..a5b8d03db0fc88c42e38cdde13a6cd2b14c06581 100644 (file)
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -114,6 +114,9 @@ do
                valgrind=t; verbose=t; shift ;;
        --tee)
                shift ;; # was handled already
+       --root=*)
+               root=$(expr "z$1" : 'z[^=]*=\(.*\)')
+               shift ;;
        *)
                echo "error: unknown test option '$1'" >&2; exit 1 ;;
        esac
@@ -645,7 +648,11 @@ fi
 
 # Test repository
 test="trash directory.$(basename "$0" .sh)"
-TRASH_DIRECTORY="$TEST_DIRECTORY/$test"
+test -n "$root" && test="$root/$test"
+case "$test" in
+/*) TRASH_DIRECTORY="$test" ;;
+ *) TRASH_DIRECTORY="$TEST_DIRECTORY/$test" ;;
+esac
 test ! -z "$debug" || remove_trash=$TRASH_DIRECTORY
 rm -fr "$test" || {
        GIT_EXIT_OK=t