check-style: Use run() instead of Popen()

The Python docs recommends using run() for all use-cases it can handle:
https://docs.python.org/3/library/subprocess.html#using-the-subprocess-module

run() waits for the subprocess started to complete, so it's not
necessary to use wait() and communicate() anymore. This simplifies the
script.

Previously running "check-style.py -r" after each commit in an
interactive rebase failed, b/c the script did not wait for the amend
command to complete. Using run() instead of Popen() solves this issue.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2733>

check-style.py

@@ -11,9 +11,13 @@ import tempfile
 uncrustify_cfg = 'tools/uncrustify.cfg'
 
 def run_diff(sha):
-    proc = subprocess.Popen(["git", "diff", "-U0", "--function-context", sha, "HEAD"], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-    files = proc.stdout.read().strip().decode('utf-8')
-    return files.split('\n')
+    proc = subprocess.run(
+        ["git", "diff", "-U0", "--function-context", sha, "HEAD"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        encoding="utf-8",
+    )
+    return proc.stdout.strip().splitlines()
 
 def find_chunks(diff):
     file_entry_re = re.compile('^\+\+\+ b/(.*)$')
@@ -76,9 +80,11 @@ def reformat_chunks(chunks, rewrite):
         tmp = create_temp_file(chunk['file'], chunk['start'], chunk['end'])
 
         # uncrustify chunk
-        proc = subprocess.Popen(["uncrustify", "-c", uncrustify_cfg, "-f", tmp.name], stdout=subprocess.PIPE)
-        reindented = proc.stdout.readlines()
-        proc.wait()
+        proc = subprocess.run(
+            ["uncrustify", "-c", uncrustify_cfg, "-f", tmp.name],
+            stdout=subprocess.PIPE,
+        )
+        reindented = proc.stdout.splitlines(keepends=True)
         if proc.returncode != 0:
             continue
 
@@ -89,18 +95,25 @@ def reformat_chunks(chunks, rewrite):
 
         if dry_run is True:
             # Show changes
-            proc = subprocess.Popen(["diff", "-up", "--color=always", chunk['file'], formatted.name], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-            diff = proc.stdout.read().decode('utf-8')
+            proc = subprocess.run(
+                ["diff", "-up", "--color=always", chunk['file'], formatted.name],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.STDOUT,
+                encoding="utf-8",
+            )
+            diff = proc.stdout
             if diff != '':
                 output = re.sub('\t', '↦\t', diff)
                 print(output)
                 changed = True
         else:
             # Apply changes
-            diff = subprocess.Popen(["diff", "-up", chunk['file'], formatted.name], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-            patch = subprocess.Popen(["patch", chunk['file']], stdin=diff.stdout)
-            diff.stdout.close()
-            patch.communicate()
+            diff = subprocess.run(
+                ["diff", "-up", chunk['file'], formatted.name],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.STDOUT,
+            )
+            patch = subprocess.run(["patch", chunk['file']], input=diff.stdout)
 
         formatted.close()
 
@@ -130,7 +143,7 @@ chunks = find_chunks(diff)
 changed = reformat_chunks(chunks, rewrite)
 
 if dry_run is not True and rewrite is True:
-    proc = subprocess.Popen(["git", "commit", "--all", "--amend", "-C", "HEAD"], stdout=subprocess.DEVNULL)
+    subprocess.run(["git", "commit", "--all", "--amend", "-C", "HEAD"], stdout=subprocess.DEVNULL)
     os._exit(0)
 elif dry_run is True and changed is True:
     print ("\nIssue the following command in your local tree to apply the suggested changes (needs uncrustify installed):\n\n $ git rebase origin/main --exec \"./check-style.py -r\" \n")