[PATCH v3 2/9] Makefiles: add "shared.mak", move ".DELETE_ON_ERROR" to it

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

We have various behavior that's shared across our Makefiles, or that
really should be (e.g. via defined templates). Let's create a
top-level "shared.mak" to house those sorts of things, and start by
adding the ".DELETE_ON_ERROR" flag to it.

See my own 7b76d6bf221 (Makefile: add and use the ".DELETE_ON_ERROR"
flag, 2021-06-29) and db10fc6c09f (doc: simplify Makefile using
.DELETE_ON_ERROR, 2021-05-21) for the addition and use of the
".DELETE_ON_ERROR" flag.

This does have the potential downside that if e.g. templates/Makefile
would like to include this "shared.mak" in the future the semantics of
such a Makefile will change, but as noted in the above commits (and
GNU make's own documentation) any such change would be for the better,
so it's safe to do this.

This also doesn't introduce a bug by e.g. having this
".DELETE_ON_ERROR" flag only apply to this new shared.mak, Makefiles
have no such scoping semantics.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Documentation/Makefile    |  6 +++---
 Makefile                  | 13 +++----------
 contrib/scalar/Makefile   |  3 +++
 contrib/scalar/t/Makefile |  3 +++
 shared.mak                |  9 +++++++++
 t/Makefile                |  3 +++
 t/interop/Makefile        |  3 +++
 t/perf/Makefile           |  3 +++
 templates/Makefile        |  3 +++
 9 files changed, 33 insertions(+), 13 deletions(-)
 create mode 100644 shared.mak

diff --git a/Documentation/Makefile b/Documentation/Makefile
index ed656db2ae9..ba27456c86a 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../shared.mak
+
 # Guard against environment variables
 MAN1_TXT =
 MAN5_TXT =
@@ -524,7 +527,4 @@ doc-l10n install-l10n::
 	$(MAKE) -C po $@
 endif
 
-# Delete the target file on error
-.DELETE_ON_ERROR:
-
 .PHONY: FORCE
diff --git a/Makefile b/Makefile
index 6f0b4b775fe..d378ec22545 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include shared.mak
+
 # The default target of this Makefile is...
 all::
 
@@ -2194,16 +2197,6 @@ shell_compatibility_test: please_set_SHELL_PATH_to_a_more_modern_shell
 strip: $(PROGRAMS) git$X
 	$(STRIP) $(STRIP_OPTS) $^
 
-### Flags affecting all rules
-
-# A GNU make extension since gmake 3.72 (released in late 1994) to
-# remove the target of rules if commands in those rules fail. The
-# default is to only do that if make itself receives a signal. Affects
-# all targets, see:
-#
-#    info make --index-search=.DELETE_ON_ERROR
-.DELETE_ON_ERROR:
-
 ### Target-specific flags and dependencies
 
 # The generic compilation pattern rule and automatically
diff --git a/contrib/scalar/Makefile b/contrib/scalar/Makefile
index 5b12a437426..6fb5cc8b701 100644
--- a/contrib/scalar/Makefile
+++ b/contrib/scalar/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../../shared.mak
+
 QUIET_SUBDIR0  = +$(MAKE) -C # space to separate -C and subdir
 QUIET_SUBDIR1  =
 
diff --git a/contrib/scalar/t/Makefile b/contrib/scalar/t/Makefile
index 6170672bb37..01e82e56d15 100644
--- a/contrib/scalar/t/Makefile
+++ b/contrib/scalar/t/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../../../shared.mak
+
 # Run scalar tests
 #
 # Copyright (c) 2005,2021 Junio C Hamano, Johannes Schindelin
diff --git a/shared.mak b/shared.mak
new file mode 100644
index 00000000000..0170bb397ae
--- /dev/null
+++ b/shared.mak
@@ -0,0 +1,9 @@
+### Flags affecting all rules
+
+# A GNU make extension since gmake 3.72 (released in late 1994) to
+# remove the target of rules if commands in those rules fail. The
+# default is to only do that if make itself receives a signal. Affects
+# all targets, see:
+#
+#    info make --index-search=.DELETE_ON_ERROR
+.DELETE_ON_ERROR:
diff --git a/t/Makefile b/t/Makefile
index 46cd5fc5273..056ce55dcc9 100644
--- a/t/Makefile
+++ b/t/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../shared.mak
+
 # Run tests
 #
 # Copyright (c) 2005 Junio C Hamano
diff --git a/t/interop/Makefile b/t/interop/Makefile
index 31a4bbc716a..6911c2915a7 100644
--- a/t/interop/Makefile
+++ b/t/interop/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../../shared.mak
+
 -include ../../config.mak
 export GIT_TEST_OPTIONS
 
diff --git a/t/perf/Makefile b/t/perf/Makefile
index 2465770a782..e4808aebed0 100644
--- a/t/perf/Makefile
+++ b/t/perf/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../../shared.mak
+
 -include ../../config.mak
 export GIT_TEST_OPTIONS
 
diff --git a/templates/Makefile b/templates/Makefile
index d22a71a3999..636cee52f51 100644
--- a/templates/Makefile
+++ b/templates/Makefile
@@ -1,3 +1,6 @@
+# Import tree-wide shared Makefile behavior and libraries
+include ../shared.mak
+
 # make and install sample templates
 
 ifndef V
-- 
2.35.1.1175.gf9e1b23ea35