doc: extensions: link-roles: hide stderr for git describe

Redirect stderr to DEVNULL when running `git describe --exact-match`.
This prevents messages like "fatal: No names found, cannot describe
anything." to be shown.

Signed-off-by: Gerard Marull-Paretas <[email protected]>

Author: gmarull

doc/_extensions/zephyr/link-roles.py

@@ -21,7 +21,8 @@
 
 def get_github_rev():
     try:
-        output = subprocess.check_output('git describe --exact-match', shell=True)
+        output = subprocess.check_output('git describe --exact-match',
+                                         shell=True, stderr=subprocess.DEVNULL)
     except subprocess.CalledProcessError:
         return 'main'