meson: fix version generation from git

run_command() was only run at configure time, meaning the generated
version (that was passed on to the sources via -DFUZZEL_VERSION)
became stale.

Fix by implementing a shell script that generates a header file, and
wrap this in a custom target that is run every time (but the generated
file is only updated when the version changes)

doc/meson.build

@@ -1,3 +1,5 @@
+sh = find_program('sh', native: true)
+
 scdoc = dependency('scdoc', native: true)
 scdoc_prog = find_program(scdoc.get_pkgconfig_variable('scdoc'), native: true)
 

generate-version.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+
+set -e
+
+default_version=${1}
+src_dir=${2}
+out_file=${3}
+
+# echo "default version:  ${default_version}"
+# echo "source directory: ${src_dir}"
+# echo "output file:      ${out_file}"
+
+if command -v git > /dev/null; then
+    workdir=$(pwd)
+    cd "${src_dir}"
+    git_version=$(git describe --always --tags)
+    git_branch=$(git rev-parse --abbrev-ref HEAD)
+    cd "${workdir}"
+
+    new_version="${git_version} ($(env LC_TIME=C date "+%b %d %Y"), branch '${git_branch}')"
+else
+    new_version="${default_version}"
+fi
+
+new_version="#define FOOT_VERSION \"${new_version}\""
+
+if [ -f "${out_file}" ]; then
+    old_version=$(cat "${out_file}")
+else
+    old_version=""
+fi
+
+# echo "old version: ${old_version}"
+# echo "new version: ${new_version}"
+
+if [ "${old_version}" != "${new_version}" ]; then
+    echo "${new_version}" > "${out_file}"
+fi

main.c

@@ -39,6 +39,7 @@
 #include "slave.h"
 #include "terminal.h"
 #include "tokenize.h"
+#include "version.h"
 #include "vt.h"
 
 #define min(x, y) ((x) < (y) ? (x) : (y))

meson.build

@@ -1,6 +1,7 @@
 project('foot', 'c',
         version: '0.9.0',
         license: 'MIT',
+        meson_version: '>=0.47.0',
         default_options: [
           'c_std=c11',
           'warning_level=1',
@@ -9,32 +10,8 @@ project('foot', 'c',
 
 is_debug_build = get_option('buildtype').startswith('debug')
 
-version = '"@0@"'.format(meson.project_version())
-
-sh = find_program('sh', native: true)
-git = find_program('git', required: false, native: true)
-
-if git.found()
-  commit_hash = run_command(
-    [sh.path(), '-c',
-     '@0@ --git-dir="$MESON_SOURCE_ROOT/.git" describe --always --tags'.format(
-       git.path())])
-
-  branch = run_command(
-    [sh.path(), '-c',
-     '@0@ --git-dir="$MESON_SOURCE_ROOT/.git" rev-parse --abbrev-ref HEAD'.format(
-       git.path())])
-
-  if commit_hash.returncode() == 0 and branch.returncode() == 0
-    version = '"@0@ (" __DATE__ ", branch \'@1@\')"'.format(
-      commit_hash.stdout().strip(), branch.stdout().strip())
-  endif
-endif
-
 add_project_arguments(
-  ['-D_GNU_SOURCE=200809L',
-   '-DFOOT_VERSION=@0@'.format(version)] +
-  (is_debug_build ? ['-D_DEBUG'] : []),
+  ['-D_GNU_SOURCE=200809L'] + (is_debug_build ? ['-D_DEBUG'] : []),
   language: 'c',
 )
 
@@ -78,6 +55,13 @@ foreach prot : [
     command: [wscanner_prog, 'private-code', '@INPUT@', '@OUTPUT@'])
 endforeach
 
+generate_version_sh = files('generate-version.sh')
+version = custom_target(
+  'generate_version',
+  build_always_stale: true,
+  output: 'version.h',
+  command: [generate_version_sh, meson.project_version(), '@SOURCE_DIR@', '@OUTPUT@'])
+
 executable(
   'foot',
   'base64.c', 'base64.h',
@@ -99,7 +83,7 @@ executable(
   'tokenize.c', 'tokenize.h',
   'tllist.h',
   'vt.c', 'vt.h',
-  wl_proto_src + wl_proto_headers,
+  wl_proto_src + wl_proto_headers, version,
   dependencies: [threads, math, freetype, fontconfig, pixman, wayland_client, wayland_cursor, xkb],
   install: true)