cmake: avoid editing t/test-lib.sh

In 7f5397a07c6c (cmake: support for testing git when building out of the
source tree, 2020-06-26), we implemented support for running Git's test
scripts even after building Git in a different directory than the source
directory.

The way we did this was to edit the file `t/test-lib.sh` to override
`GIT_BUILD_DIR` to point somewhere else than the parent of the `t/`
directory.

This is unideal because it always leaves a tracked file marked as
modified, and it is all too easy to commit that change by mistake.

Let's change the strategy by teaching `t/test-lib.sh` to detect the
presence of a file called `GIT-BUILD-DIR` in the source directory. If it
exists, the contents are interpreted as the location to the _actual_
build directory. We then write this file as part of the CTest
definition.

To support building Git via a regular `make` invocation after building
it using CMake, we ensure that the `GIT-BUILD-DIR` file is deleted (for
convenience, this is done as part of the Makefile rule that is already
run with every `make` invocation to ensure that `GIT-BUILD-OPTIONS` is
up to date).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 04d0fd1fe6..9347ed90da 100644
--- a/Makefile
+++ b/Makefile
@@ -3028,6 +3028,7 @@ else
 	@echo RUNTIME_PREFIX=\'false\' >>$@+
 endif
 	@if cmp $@+ $@ >/dev/null 2>&1; then $(RM) $@+; else mv $@+ $@; fi
+	@if test -f GIT-BUILD-DIR; then rm GIT-BUILD-DIR; fi
 
 ### Detect Python interpreter path changes
 ifndef NO_PYTHON