[tools] Flush stdout before reading input

The last line of output (which is not terminated by a newline) was not
showing for me when running the merge script. We can either fix it by
specifying `flush=True` at the `print` statement, or flushing before
reading user input. The latter seems more future-proof.

R=machenbach@chromium.org

Change-Id: I61cb929d2f7cdd20b3e32b9beb1653fe2d5c5791
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3676857Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80890}

tools/release/common_includes.py

@@ -114,15 +114,15 @@ def Command(cmd, args="", prefix="", pipe=True, cwd=None):
 
 
 def SanitizeVersionTag(tag):
-    version_without_prefix = re.compile(r"^\d+\.\d+\.\d+(?:\.\d+)?$")
-    version_with_prefix = re.compile(r"^tags\/\d+\.\d+\.\d+(?:\.\d+)?$")
-
-    if version_without_prefix.match(tag):
-      return tag
-    elif version_with_prefix.match(tag):
-        return tag[len("tags/"):]
-    else:
-      return None
+  version_without_prefix = re.compile(r"^\d+\.\d+\.\d+(?:\.\d+)?$")
+  version_with_prefix = re.compile(r"^tags\/\d+\.\d+\.\d+(?:\.\d+)?$")
+
+  if version_without_prefix.match(tag):
+    return tag
+  elif version_with_prefix.match(tag):
+    return tag[len("tags/"):]
+  else:
+    return None
 
 
 def NormalizeVersionTags(version_tags):
@@ -146,6 +146,7 @@ class SideEffectHandler(object):  # pragma: no cover
     return Command(cmd, args, prefix, pipe, cwd=cwd)
 
   def ReadLine(self):
+    sys.stdout.flush()
     return sys.stdin.readline().strip()
 
   def ReadURL(self, url, params=None):
@@ -238,7 +239,7 @@ class GitInterface(VCInterface):
     self.step.Git("fetch")
 
   def GetTags(self):
-     return self.step.Git("tag").strip().splitlines()
+    return self.step.Git("tag").strip().splitlines()
 
   def GetBranches(self):
     # Get relevant remote branches, e.g. "branch-heads/3.25".
@@ -684,18 +685,22 @@ class UploadStep(Step):
 
 def MakeStep(step_class=Step, number=0, state=None, config=None,
              options=None, side_effect_handler=DEFAULT_SIDE_EFFECT_HANDLER):
-    # Allow to pass in empty dictionaries.
-    state = state if state is not None else {}
-    config = config if config is not None else {}
-
-    try:
-      message = step_class.MESSAGE
-    except AttributeError:
-      message = step_class.__name__
+  # Allow to pass in empty dictionaries.
+  state = state if state is not None else {}
+  config = config if config is not None else {}
 
-    return step_class(message, number=number, config=config,
-                      state=state, options=options,
-                      handler=side_effect_handler)
+  try:
+    message = step_class.MESSAGE
+  except AttributeError:
+    message = step_class.__name__
+
+  return step_class(
+      message,
+      number=number,
+      config=config,
+      state=state,
+      options=options,
+      handler=side_effect_handler)
 
 
 class ScriptsBase(object):