git_sha1_gen.py: fix out-of-date comment

[mesa.git] / bin / git_sha1_gen.py

diff --git a/bin/git_sha1_gen.py b/bin/git_sha1_gen.py
old mode 100755 (executable)
new mode 100644 (file)
index e26d3a3..7fb5c99
--- a/bin/git_sha1_gen.py
+++ b/bin/git_sha1_gen.py
@@ -1,20 +1,49 @@
-#!/usr/bin/env python
+"""
+Generate the contents of the git_sha1.h file.
+"""
 
+
+import argparse
+import os
 import os.path
 import subprocess
 import sys
 
-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',
-        '--short=10',
-        'HEAD',
-    ], stderr=open(os.devnull, 'w'))
-except:
-    # don't print anything if it fails
-    pass
+
+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:
+        # 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:
-    sys.stdout.write('#define MESA_GIT_SHA1 "git-%s"\n' % git_sha1.rstrip())
+    write_if_different('#define MESA_GIT_SHA1 ""')