[PATCH 5/9] test-lib.sh: support a "GIT_TEST_BUILD_DIR"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Compliment the existing GIT_TEST_INSTALLED variable added in [1] with
one that allows for testing a git built in a directory that's not
"../".

Instead of "test this installed git" ("GIT_TEST_INSTALLED"), this new
"GIT_TEST_BUILD_DIR" is a "test this built directory over
there". E.g. this will pass all tests:

	git clone --depth=1 https://github.com/git/git.git git1
	cp -R git1 git2
	make -C git1
	[apply this change to git2]
	(cd git2 && GIT_TEST_BUILD_DIR="$PWD/../git1" make -C t prove)

1. 6720721e152 (test-lib.sh: Allow running the test suite against
   installed git, 2009-03-16)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 t/README      | 3 +++
 t/test-lib.sh | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/t/README b/t/README
index 979b2d4833d..fc0daef2e41 100644
--- a/t/README
+++ b/t/README
@@ -231,6 +231,9 @@ override the location of the dashed-form subcommands (what
 GIT_EXEC_PATH would be used for during normal operation).
 GIT_TEST_EXEC_PATH defaults to `$GIT_TEST_INSTALLED/git --exec-path`.
 
+Similar to GIT_TEST_INSTALLED, GIT_TEST_BUILD_DIR can be pointed to
+another git.git checkout's build directory, to test its built binaries
+against the tests in this checkout.
 
 Skipping Tests
 --------------
diff --git a/t/test-lib.sh b/t/test-lib.sh
index d2e5dee6c89..41b1ddc96ff 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -47,6 +47,10 @@ fi
 # its build directory.
 GIT_SOURCE_DIR="${TEST_DIRECTORY%/t}"
 GIT_BUILD_DIR="$GIT_SOURCE_DIR"
+if test -n "$GIT_TEST_BUILD_DIR"
+then
+	GIT_BUILD_DIR="$GIT_TEST_BUILD_DIR"
+fi
 
 if test "$TEST_DIRECTORY" = "$GIT_BUILD_DIR"
 then
-- 
2.38.0.1205.gcea0601d673