Makefile: refactor GIT-VERSION-GEN to be reusable

Our "GIT-VERSION-GEN" script always writes the "GIT-VERSION-FILE" into
the current directory, where the expectation is that it should exist in
the source directory. But other build systems that support out-of-tree
builds may not want to do that to keep the source directory pristine,
even though CMake currently doesn't care.

Refactor the script such that it won't write the "GIT-VERSION-FILE"
directly anymore, but instead knows to replace @PLACEHOLDERS@ in an
arbitrary input file. This allows us to simplify the logic in CMake to
determine the project version, but can also be reused later on in order
to generate other files that need to contain version information like
our "git.rc" file.

While at it, change the format of the version file by removing the
spaces around the equals sign. Like this we can continue to include the
file in our Makefiles, but can also start to source it in shell scripts
in subsequent steps.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

GIT-VERSION-FILE.in

@@ -0,0 +1 @@
+GIT_VERSION=@GIT_VERSION@

GIT-VERSION-GEN

@@ -1,23 +1,48 @@
 #!/bin/sh
 
-GVF=GIT-VERSION-FILE
 DEF_VER=v2.47.GIT
 
 LF='
 '
 
+if test "$#" -ne 3
+then
+    echo >&2 "USAGE: $0 <SOURCE_DIR> <INPUT> <OUTPUT>"
+    exit 1
+fi
+
+SOURCE_DIR="$1"
+INPUT="$2"
+OUTPUT="$3"
+
+if ! test -f "$INPUT"
+then
+	echo >&2 "Input is not a file: $INPUT"
+	exit 1
+fi
+
+# Protect us from reading Git version information outside of the Git directory
+# in case it is not a repository itself, but embedded in an unrelated
+# repository.
+GIT_CEILING_DIRECTORIES="$SOURCE_DIR/.."
+export GIT_CEILING_DIRECTORIES
+
 # First see if there is a version file (included in release tarballs),
 # then try git-describe, then default.
-if test -f version
+if test -f "$SOURCE_DIR"/version
 then
-	VN=$(cat version) || VN="$DEF_VER"
-elif { test -d "${GIT_DIR:-.git}" || test -f .git; } &&
-	VN=$(git describe --match "v[0-9]*" HEAD 2>/dev/null) &&
+	VN=$(cat "$SOURCE_DIR"/version) || VN="$DEF_VER"
+elif {
+		test -d "$SOURCE_DIR/.git" ||
+		test -d "${GIT_DIR:-.git}" ||
+		test -f "$SOURCE_DIR"/.git;
+	} &&
+	VN=$(git -C "$SOURCE_DIR" describe --match "v[0-9]*" HEAD 2>/dev/null) &&
 	case "$VN" in
 	*$LF*) (exit 1) ;;
 	v[0-9]*)
-		git update-index -q --refresh
-		test -z "$(git diff-index --name-only HEAD --)" ||
+		git -C "$SOURCE_DIR" update-index -q --refresh
+		test -z "$(git -C "$SOURCE_DIR" diff-index --name-only HEAD --)" ||
 		VN="$VN-dirty" ;;
 	esac
 then
@@ -26,15 +51,21 @@ else
 	VN="$DEF_VER"
 fi
 
-VN=$(expr "$VN" : v*'\(.*\)')
+GIT_VERSION=$(expr "$VN" : v*'\(.*\)')
 
-if test -r $GVF
+read GIT_MAJOR_VERSION GIT_MINOR_VERSION GIT_MICRO_VERSION trailing <<EOF
+$(echo "$GIT_VERSION" 0 0 0 | tr '.a-zA-Z-' ' ')
+EOF
+
+sed -e "s|@GIT_VERSION@|$GIT_VERSION|" \
+	-e "s|@GIT_MAJOR_VERSION@|$GIT_MAJOR_VERSION|" \
+	-e "s|@GIT_MINOR_VERSION@|$GIT_MINOR_VERSION|" \
+	-e "s|@GIT_MICRO_VERSION@|$GIT_MICRO_VERSION|" \
+	"$INPUT" >"$OUTPUT"+
+
+if ! test -f "$OUTPUT" || ! cmp "$OUTPUT"+ "$OUTPUT" >/dev/null
 then
-	VC=$(sed -e 's/^GIT_VERSION = //' <$GVF)
+	mv "$OUTPUT"+ "$OUTPUT"
 else
-	VC=unset
+	rm "$OUTPUT"+
 fi
-test "$VN" = "$VC" || {
-	echo >&2 "GIT_VERSION = $VN"
-	echo "GIT_VERSION = $VN" >$GVF
-}

Makefile

@@ -592,7 +592,10 @@ include shared.mak
 #        Disable -pedantic compilation.
 
 GIT-VERSION-FILE: FORCE
-	@$(SHELL_PATH) ./GIT-VERSION-GEN
+	@OLD=$$(cat $@ 2>/dev/null || :) && \
+	$(SHELL_PATH) ./GIT-VERSION-GEN "$(shell pwd)" GIT-VERSION-FILE.in $@ && \
+	NEW=$$(cat $@ 2>/dev/null || :) && \
+	if test "$$OLD" != "$$NEW"; then echo "$$NEW" >&2; fi
 -include GIT-VERSION-FILE
 
 # Set our default configuration.

ci/test-documentation.sh

@@ -6,7 +6,7 @@
 . ${0%/*}/lib.sh
 
 filter_log () {
-	sed -e '/^GIT_VERSION = /d' \
+	sed -e '/^GIT_VERSION=/d' \
 	    -e "/constant Gem::ConfigMap is deprecated/d" \
 	    -e '/^    \* new asciidoc flags$/d' \
 	    -e '/stripped namespace before processing/d' \

contrib/buildsystems/CMakeLists.txt

@@ -83,23 +83,12 @@ if(NOT SH_EXE)
 			"On Windows, you can get it as part of 'Git for Windows' install at https://gitforwindows.org/")
 endif()
 
-#Create GIT-VERSION-FILE using GIT-VERSION-GEN
-if(NOT EXISTS ${CMAKE_SOURCE_DIR}/GIT-VERSION-FILE)
-	message("Generating GIT-VERSION-FILE")
-	execute_process(COMMAND ${SH_EXE} ${CMAKE_SOURCE_DIR}/GIT-VERSION-GEN
-		WORKING_DIRECTORY ${CMAKE_SOURCE_DIR})
-endif()
-
-#Parse GIT-VERSION-FILE to get the version
-file(STRINGS ${CMAKE_SOURCE_DIR}/GIT-VERSION-FILE git_version REGEX "GIT_VERSION = (.*)")
-string(REPLACE "GIT_VERSION = " "" git_version ${git_version})
-string(FIND ${git_version} "GIT" location)
-if(location EQUAL -1)
-	string(REGEX MATCH "[0-9]*\\.[0-9]*\\.[0-9]*" git_version ${git_version})
-else()
-	string(REGEX MATCH "[0-9]*\\.[0-9]*" git_version ${git_version})
-	string(APPEND git_version ".0") #for building from a snapshot
-endif()
+message("Generating Git version")
+execute_process(COMMAND ${SH_EXE} "${CMAKE_SOURCE_DIR}/GIT-VERSION-GEN"
+		"${CMAKE_SOURCE_DIR}"
+		"${CMAKE_SOURCE_DIR}/contrib/buildsystems/git-version.in"
+		"${CMAKE_BINARY_DIR}/git-version")
+file(STRINGS "${CMAKE_BINARY_DIR}/git-version" git_version)
 
 project(git
 	VERSION ${git_version}

contrib/buildsystems/git-version.in

@@ -0,0 +1 @@
+@GIT_MAJOR_VERSION@.@GIT_MINOR_VERSION@.@GIT_MICRO_VERSION@