Set tracing to always on and save to .repo/TRACE_FILE.

- add `--trace_to_stderr` option so stderr will include trace outputs and any other errors that get sent to stderr
- while TRACE_FILE will only include trace outputs

piggy-backing on: https://gerrit-review.googlesource.com/c/git-repo/+/349154

Change-Id: I3895a84de4b2784f17fac4325521cd5e72e645e2
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/350114
Reviewed-by: LaMont Jones <lamontjones@google.com>
Tested-by: Joanna Wang <jojwang@google.com>

project.py

@@ -41,7 +41,7 @@ from error import ManifestInvalidRevisionError, ManifestInvalidPathError
 from error import NoManifestException, ManifestParseError
 import platform_utils
 import progress
-from repo_trace import IsTrace, Trace
+from repo_trace import Trace
 
 from git_refs import GitRefs, HEAD, R_HEADS, R_TAGS, R_PUB, R_M, R_WORKTREE_M
 
@@ -2416,16 +2416,16 @@ class Project(object):
         srcUrl = 'http' + srcUrl[len('persistent-http'):]
       cmd += [srcUrl]
 
-      if IsTrace():
-        Trace('%s', ' '.join(cmd))
-      if verbose:
-        print('%s: Downloading bundle: %s' % (self.name, srcUrl))
-      stdout = None if verbose else subprocess.PIPE
-      stderr = None if verbose else subprocess.STDOUT
-      try:
-        proc = subprocess.Popen(cmd, stdout=stdout, stderr=stderr)
-      except OSError:
-        return False
+      proc = None
+      with Trace('Fetching bundle: %s', ' '.join(cmd)):
+        if verbose:
+          print('%s: Downloading bundle: %s' % (self.name, srcUrl))
+        stdout = None if verbose else subprocess.PIPE
+        stderr = None if verbose else subprocess.STDOUT
+        try:
+          proc = subprocess.Popen(cmd, stdout=stdout, stderr=stderr)
+        except OSError:
+          return False
 
       (output, _) = proc.communicate()
       curlret = proc.returncode