build: Expand version info in SDL_REVISION and SDL_GetRevision()

Instead of using a URL and git sha1, this uses `git describe` to
describe the version relative to the nearest previous git tag, which
gives a better indication of whether this is a release, a prerelease,
a slightly patched prerelease, or a long way after the last release
during active development.

This serves two purposes: it makes those APIs more informative, and it
also puts this information into the binary in a form that is easy to
screen-scrape using strings(1). For instance, if the bundled version of
SDL in a game has this, we can see at a glance what version it is.

It's also shorter than using the web address of the origin git
repository and the full git commit sha1.

Also write the computed version into a file ./VERSION in `make dist`
tarballs, so that when we build from a tarball on a system that doesn't
have git available, we still get the version details.

For the Perforce code path in showrev.sh, output the version number
followed by the Perforce revision, in a format reminiscent of
`git describe` (with p instead of g to indicate Perforce).

For the code path with no VCS available at all, put a suffix on the
version number to indicate that this is just a guess (we can't know
whether this SDL version is actually a git snapshot or has been
patched locally or similar).

Resolves: https://github.com/libsdl-org/SDL/issues/6418
Signed-off-by: Simon McVittie <smcv@collabora.com>

.gitignore

@@ -15,6 +15,7 @@ build
 gen
 Build
 buildbot
+/VERSION
 
 *.so
 *.so.*

CMakeLists.txt

@@ -2930,29 +2930,36 @@ listtostr(EXTRA_CFLAGS _EXTRA_CFLAGS)
 set(EXTRA_CFLAGS ${_EXTRA_CFLAGS})
 
 # Compat helpers for the configuration files
+
+if(EXISTS "${PROJECT_SOURCE_DIR}/VERSION")
+  file(READ "${PROJECT_SOURCE_DIR}/VERSION" SDL_SOURCE_VERSION)
+endif()
+
 find_package(Git)
 if(Git_FOUND)
   execute_process(COMMAND
-    "${GIT_EXECUTABLE}" remote get-url origin
-    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
-    RESULT_VARIABLE GIT_URL_STATUS
-    OUTPUT_VARIABLE GIT_URL
-    ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
-
-  execute_process(COMMAND
-    "${GIT_EXECUTABLE}" rev-list --max-count=1 HEAD~..
-    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+    "${GIT_EXECUTABLE}" describe --always --tags --long
+    WORKING_DIRECTORY "${PROJECT_SOURCE_DIR}"
     RESULT_VARIABLE GIT_REVISION_STATUS
     OUTPUT_VARIABLE GIT_REVISION
     ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
-
-  if(GIT_URL_STATUS EQUAL 0 OR GIT_REVISION_STATUS EQUAL 0)
-    set(SDL_REVISION "${GIT_URL}@${GIT_REVISION}")
 else()
-    set(SDL_REVISION "")
+  set(GIT_REVISION_STATUS 1)
+  set(GIT_REVISION "")
+endif()
+
+if(SDL_SOURCE_VERSION)
+  set(SDL_REVISION "SDL-${SDL_SOURCE_VERSION}")
+elseif(GIT_REVISION_STATUS EQUAL 0)
+  if(GIT_REVISION MATCHES "^[0-9a-f]+$")
+    # Just a truncated sha1, so prefix it with the version number
+    set(SDL_REVISION "SDL-${SDL_VERSION}-g${GIT_REVISION}")
+  else()
+    # e.g. release-2.24.0-542-g96361fc47
+    set(SDL_REVISION "SDL-${GIT_REVISION}")
   endif()
 else()
-  set(SDL_REVISION "")
+  set(SDL_REVISION "SDL-${SDL_VERSION}-no-vcs")
 endif()
 
 configure_file("${SDL2_SOURCE_DIR}/include/SDL_revision.h.cmake"

Makefile.in

@@ -252,7 +252,7 @@ dist $(distfile):
 	    -name '.#*' \) \
 	    -exec rm -f {} \;
 	if test -f $(distdir)/test/Makefile; then (cd $(distdir)/test && make distclean); fi
-	(cd $(distdir); build-scripts/updaterev.sh)
+	(cd $(distdir); $(srcdir)/build-scripts/updaterev.sh --dist)
 	tar cvf - $(distdir) | gzip --best >$(distfile)
 	rm -rf $(distdir)
 

build-scripts/showrev.sh

@@ -5,10 +5,31 @@
 SDL_ROOT=$(dirname $0)/..
 cd $SDL_ROOT
 
+if [ -e ./VERSION ]; then
+    cat ./VERSION
+    exit 0
+fi
+
+major=$(sed -ne 's/^#define SDL_MAJOR_VERSION  *//p' include/SDL_version.h)
+minor=$(sed -ne 's/^#define SDL_MINOR_VERSION  *//p' include/SDL_version.h)
+micro=$(sed -ne 's/^#define SDL_PATCHLEVEL  *//p' include/SDL_version.h)
+version="${major}.${minor}.${micro}"
+
 if [ -x "$(command -v git)" ]; then
-    rev=$(echo "$(git remote get-url origin 2>/dev/null)@$(git rev-list HEAD~.. 2>/dev/null)")
-    if [ "$rev" != "@" ]; then
-        echo $rev
+    rev="$(git describe --tags --long 2>/dev/null)"
+    if [ -n "$rev" ]; then
+        # e.g. release-2.24.0-542-g96361fc47
+        # or release-2.24.1-5-g36b987dab
+        # or prerelease-2.23.2-0-gcb46e1b3f
+        echo "$rev"
+        exit 0
+    fi
+
+    rev="$(git describe --always --tags --long 2>/dev/null)"
+    if [ -n "$rev" ]; then
+        # Just a truncated sha1, e.g. 96361fc47.
+        # Turn it into e.g. 2.25.0-g96361fc47
+        echo "${version}-g${rev}"
         exit 0
     fi
 fi
@@ -16,10 +37,12 @@ fi
 if [ -x "$(command -v p4)" ]; then
     rev="$(p4 changes -m1 ./...\#have 2>/dev/null| awk '{print $2}')"
     if [ $? = 0 ]; then
-        echo $rev
+        # e.g. 2.25.0-p7511446
+        echo "${version}-p${rev}"
         exit 0
     fi
 fi
 
-echo ""
-exit 1
+# best we can do
+echo "${version}-no-vcs"
+exit 0

build-scripts/updaterev.sh

@@ -6,10 +6,28 @@ outdir=`pwd`
 cd `dirname $0`
 srcdir=..
 header=$outdir/include/SDL_revision.h
+dist=
+
+while [ "$#" -gt 0 ]; do
+    case "$1" in
+        (--dist)
+            dist=yes
+            shift
+            ;;
+        (*)
+            echo "$0: Unknown option: $1" >&2
+            exit 2
+            ;;
+    esac
+done
 
 rev=`sh showrev.sh 2>/dev/null`
 if [ "$rev" != "" ]; then
-    echo "#define SDL_REVISION \"$rev\"" >"$header.new"
+    if [ -n "$dist" ]; then
+        echo "$rev" > "$outdir/VERSION"
+    fi
+    echo "/* Generated by updaterev.sh, do not edit */" >"$header.new"
+    echo "#define SDL_REVISION \"SDL-$rev\"" >>"$header.new"
     echo "#define SDL_REVISION_NUMBER 0" >>"$header.new"
     if diff $header $header.new >/dev/null 2>&1; then
         rm "$header.new"

configure

@@ -32529,3 +32529,4 @@ if test -n "$ac_unrecognized_opts" && test "$enable_option_checking" != no; then
 printf "%s\n" "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
 fi
 
+

include/SDL_revision.h.cmake

@@ -1,6 +1,2 @@
-#cmakedefine SDL_REVISION "@SDL_REVISION@"
+#define SDL_REVISION "@SDL_REVISION@"
 #define SDL_REVISION_NUMBER 0
-
-#ifndef SDL_REVISION
-#define SDL_REVISION ""
-#endif

test/configure

@@ -6103,3 +6103,4 @@ if test -n "$ac_unrecognized_opts" && test "$enable_option_checking" != no; then
 printf "%s\n" "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
 fi
 
+