sync code with last improvements from OpenBSD

lib/mesa/bin/git_sha1_gen.py

@@ -0,0 +1,50 @@
+"""
+Generate the contents of the git_sha1.h file.
+"""
+
+import argparse
+import os
+import os.path
+import subprocess
+import sys
+
+
+def get_git_sha1():
+    """Try to get the git SHA1 with git rev-parse."""
+    git_dir = os.path.join(os.path.dirname(sys.argv[0]), '..', '.git')
+    try:
+        git_sha1 = subprocess.check_output([
+            'git',
+            '--git-dir=' + git_dir,
+            'rev-parse',
+            'HEAD',
+        ], stderr=open(os.devnull, 'w')).decode("ascii")
+    except Exception:
+        # don't print anything if it fails
+        git_sha1 = ''
+    return git_sha1
+
+
+def write_if_different(contents):
+    """
+    Avoid touching the output file if it doesn't need modifications
+    Useful to avoid triggering rebuilds when nothing has changed.
+    """
+    if os.path.isfile(args.output):
+        with open(args.output, 'r') as file:
+            if file.read() == contents:
+                return
+    with open(args.output, 'w') as file:
+        file.write(contents)
+
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--output', help='File to write the #define in',
+                    required=True)
+args = parser.parse_args()
+
+git_sha1 = os.environ.get('MESA_GIT_SHA1_OVERRIDE', get_git_sha1())[:10]
+if git_sha1:
+    write_if_different('#define MESA_GIT_SHA1 " (git-' + git_sha1 + ')"')
+else:
+    write_if_different('#define MESA_GIT_SHA1 ""')