Add support for GIT_CEILING_DIRECTORIES

Make git recognize a new environment variable that prevents it from
chdir'ing up into specified directories when looking for a GIT_DIR.
Useful for avoiding slow network directories.

For example, I use git in an environment where homedirs are automounted
and "ls /home/nonexistent" takes about 9 seconds.  Setting
GIT_CEILING_DIRS="/home" allows "git help -a" (for bash completion) and
"git symbolic-ref" (for my shell prompt) to run in a reasonable time.

Signed-off-by: David Reiss <dreiss@facebook.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 211 insertions, 0 deletions

diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 9076b3bd8..6e7501f35 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -12,6 +12,11 @@ norm_abs() {
 	"test \$(test-path-utils normalize_absolute_path '$1') = '$2'"
 }
 
+ancestor() {
+	test_expect_success "longest ancestor" \
+	"test \$(test-path-utils longest_ancestor_length '$1' '$2') = '$3'"
+}
+
 norm_abs "" /
 norm_abs / /
 norm_abs // /
@@ -37,4 +42,46 @@ norm_abs /d1/s1//../s2/../../d2 /d2
 norm_abs /d1/.../d2 /d1/.../d2
 norm_abs /d1/..././../d2 /d1/d2
 
+ancestor / "" -1
+ancestor / / -1
+ancestor /foo "" -1
+ancestor /foo : -1
+ancestor /foo ::. -1
+ancestor /foo ::..:: -1
+ancestor /foo / 0
+ancestor /foo /fo -1
+ancestor /foo /foo -1
+ancestor /foo /foo/ -1
+ancestor /foo /bar -1
+ancestor /foo /bar/ -1
+ancestor /foo /foo/bar -1
+ancestor /foo /foo:/bar/ -1
+ancestor /foo /foo/:/bar/ -1
+ancestor /foo /foo::/bar/ -1
+ancestor /foo /:/foo:/bar/ 0
+ancestor /foo /foo:/:/bar/ 0
+ancestor /foo /:/bar/:/foo 0
+ancestor /foo/bar "" -1
+ancestor /foo/bar / 0
+ancestor /foo/bar /fo -1
+ancestor /foo/bar foo -1
+ancestor /foo/bar /foo 4
+ancestor /foo/bar /foo/ 4
+ancestor /foo/bar /foo/ba -1
+ancestor /foo/bar /:/fo 0
+ancestor /foo/bar /foo:/foo/ba 4
+ancestor /foo/bar /bar -1
+ancestor /foo/bar /bar/ -1
+ancestor /foo/bar /fo: -1
+ancestor /foo/bar :/fo -1
+ancestor /foo/bar /foo:/bar/ 4
+ancestor /foo/bar /:/foo:/bar/ 4
+ancestor /foo/bar /foo:/:/bar/ 4
+ancestor /foo/bar /:/bar/:/fo 0
+ancestor /foo/bar /:/bar/ 0
+ancestor /foo/bar :://foo/. 4
+ancestor /foo/bar :://foo/.:: 4
+ancestor /foo/bar //foo/./::/bar 4
+ancestor /foo/bar ::/bar -1
+
 test_done
diff --git a/t/t1504-ceiling-dirs.sh b/t/t1504-ceiling-dirs.sh
new file mode 100755
index 000000000..91b704a3a
--- /dev/null
+++ b/t/t1504-ceiling-dirs.sh
@@ -0,0 +1,163 @@
+#!/bin/sh
+
+test_description='test GIT_CEILING_DIRECTORIES'
+. ./test-lib.sh
+
+test_prefix() {
+	test_expect_success "$1" \
+	"test '$2' = \"\$(git rev-parse --show-prefix)\""
+}
+
+test_fail() {
+	test_expect_code 128 "$1: prefix" \
+	"git rev-parse --show-prefix"
+}
+
+TRASH_ROOT="$(pwd)"
+ROOT_PARENT=$(dirname "$TRASH_ROOT")
+
+
+unset GIT_CEILING_DIRECTORIES
+test_prefix no_ceil ""
+
+export GIT_CEILING_DIRECTORIES
+
+GIT_CEILING_DIRECTORIES=""
+test_prefix ceil_empty ""
+
+GIT_CEILING_DIRECTORIES="$ROOT_PARENT"
+test_prefix ceil_at_parent ""
+
+GIT_CEILING_DIRECTORIES="$ROOT_PARENT/"
+test_prefix ceil_at_parent_slash ""
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT"
+test_prefix ceil_at_trash ""
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/"
+test_prefix ceil_at_trash_slash ""
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub"
+test_prefix ceil_at_sub ""
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/"
+test_prefix ceil_at_sub_slash ""
+
+
+mkdir -p sub/dir || exit 1
+cd sub/dir || exit 1
+
+unset GIT_CEILING_DIRECTORIES
+test_prefix subdir_no_ceil "sub/dir/"
+
+export GIT_CEILING_DIRECTORIES
+
+GIT_CEILING_DIRECTORIES=""
+test_prefix subdir_ceil_empty "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT"
+test_fail subdir_ceil_at_trash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/"
+test_fail subdir_ceil_at_trash_slash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub"
+test_fail subdir_ceil_at_sub
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/"
+test_fail subdir_ceil_at_sub_slash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/dir"
+test_prefix subdir_ceil_at_subdir "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/dir/"
+test_prefix subdir_ceil_at_subdir_slash "sub/dir/"
+
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/su"
+test_prefix subdir_ceil_at_su "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/su/"
+test_prefix subdir_ceil_at_su_slash "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/di"
+test_prefix subdir_ceil_at_sub_di "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub/di"
+test_prefix subdir_ceil_at_sub_di_slash "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/subdi"
+test_prefix subdir_ceil_at_subdi "sub/dir/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/subdi"
+test_prefix subdir_ceil_at_subdi_slash "sub/dir/"
+
+
+GIT_CEILING_DIRECTORIES="foo:$TRASH_ROOT/sub"
+test_fail second_of_two
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub:bar"
+test_fail first_of_two
+
+GIT_CEILING_DIRECTORIES="foo:$TRASH_ROOT/sub:bar"
+test_fail second_of_three
+
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sub"
+GIT_DIR=../../.git
+export GIT_DIR
+test_prefix git_dir_specified ""
+unset GIT_DIR
+
+
+cd ../.. || exit 1
+mkdir -p s/d || exit 1
+cd s/d || exit 1
+
+unset GIT_CEILING_DIRECTORIES
+test_prefix sd_no_ceil "s/d/"
+
+export GIT_CEILING_DIRECTORIES
+
+GIT_CEILING_DIRECTORIES=""
+test_prefix sd_ceil_empty "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT"
+test_fail sd_ceil_at_trash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/"
+test_fail sd_ceil_at_trash_slash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s"
+test_fail sd_ceil_at_s
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s/"
+test_fail sd_ceil_at_s_slash
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s/d"
+test_prefix sd_ceil_at_sd "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s/d/"
+test_prefix sd_ceil_at_sd_slash "s/d/"
+
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/su"
+test_prefix sd_ceil_at_su "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/su/"
+test_prefix sd_ceil_at_su_slash "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s/di"
+test_prefix sd_ceil_at_s_di "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/s/di"
+test_prefix sd_ceil_at_s_di_slash "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sdi"
+test_prefix sd_ceil_at_sdi "s/d/"
+
+GIT_CEILING_DIRECTORIES="$TRASH_ROOT/sdi"
+test_prefix sd_ceil_at_sdi_slash "s/d/"
+
+
+test_done
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 5002fb04b..c3a316738 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -35,6 +35,7 @@ unset GIT_WORK_TREE
 unset GIT_EXTERNAL_DIFF
 unset GIT_INDEX_FILE
 unset GIT_OBJECT_DIRECTORY
+unset GIT_CEILING_DIRECTORIES
 unset SHA1_FILE_DIRECTORIES
 unset SHA1_FILE_DIRECTORY
 GIT_MERGE_VERBOSITY=5