Address review comments (part 2: make_command).

src/pip/_internal/utils/misc.py

@@ -766,9 +766,19 @@ def unpack_file(
 
 
 def make_command(*args):
-    # type: (Union[str, HiddenText]) -> CommandArgs
+    # type: (Union[str, HiddenText, CommandArgs]) -> CommandArgs
+    """
+    Create a CommandArgs object.
+    """
     command_args = []  # type: CommandArgs
-    command_args.extend(args)
+    for arg in args:
+        # Check for list instead of CommandArgs since CommandArgs is
+        # only known during type-checking.
+        if isinstance(arg, list):
+            command_args.extend(arg)
+        else:
+            # Otherwise, arg is str or HiddenText.
+            command_args.append(arg)
 
     return command_args
 

src/pip/_internal/vcs/bazaar.py

@@ -54,7 +54,7 @@ def export(self, location, url):
 
         url, rev_options = self.get_url_rev_options(url)
         self.run_command(
-            make_command('export', location, url) + rev_options.to_args(),
+            make_command('export', location, url, rev_options.to_args()),
             show_stdout=False,
         )
 
@@ -68,7 +68,7 @@ def fetch_new(self, dest, url, rev_options):
             display_path(dest),
         )
         cmd_args = (
-            make_command('branch', '-q') + rev_options.to_args() + [url, dest]
+            make_command('branch', '-q', rev_options.to_args(), url, dest)
         )
         self.run_command(cmd_args)
 
@@ -78,7 +78,7 @@ def switch(self, dest, url, rev_options):
 
     def update(self, dest, url, rev_options):
         # type: (str, HiddenText, RevOptions) -> None
-        cmd_args = make_command('pull', '-q') + rev_options.to_args()
+        cmd_args = make_command('pull', '-q', rev_options.to_args())
         self.run_command(cmd_args, cwd=dest)
 
     @classmethod

src/pip/_internal/vcs/git.py

@@ -173,7 +173,7 @@ def resolve_revision(cls, dest, url, rev_options):
 
         # If it looks like a ref, we have to fetch it explicitly.
         cls.run_command(
-            make_command('fetch', '-q', url) + rev_options.to_args(),
+            make_command('fetch', '-q', url, rev_options.to_args()),
             cwd=dest,
         )
         # Change the revision to the SHA of the ref we fetched
@@ -211,8 +211,8 @@ def fetch_new(self, dest, url, rev_options):
                 # Only do a checkout if the current commit id doesn't match
                 # the requested revision.
                 if not self.is_commit_id_equal(dest, rev_options.rev):
-                    cmd_args = (
-                        make_command('checkout', '-q') + rev_options.to_args()
+                    cmd_args = make_command(
+                        'checkout', '-q', rev_options.to_args(),
                     )
                     self.run_command(cmd_args, cwd=dest)
             elif self.get_current_branch(dest) != branch_name:
@@ -233,7 +233,7 @@ def switch(self, dest, url, rev_options):
             make_command('config', 'remote.origin.url', url),
             cwd=dest,
         )
-        cmd_args = make_command('checkout', '-q') + rev_options.to_args()
+        cmd_args = make_command('checkout', '-q', rev_options.to_args())
         self.run_command(cmd_args, cwd=dest)
 
         self.update_submodules(dest)
@@ -248,9 +248,7 @@ def update(self, dest, url, rev_options):
             self.run_command(['fetch', '-q'], cwd=dest)
         # Then reset to wanted revision (maybe even origin/master)
         rev_options = self.resolve_revision(dest, url, rev_options)
-        cmd_args = (
-            make_command('reset', '--hard', '-q') + rev_options.to_args()
-        )
+        cmd_args = make_command('reset', '--hard', '-q', rev_options.to_args())
         self.run_command(cmd_args, cwd=dest)
         #: update submodules
         self.update_submodules(dest)

src/pip/_internal/vcs/mercurial.py

@@ -49,7 +49,7 @@ def fetch_new(self, dest, url, rev_options):
         )
         self.run_command(make_command('clone', '--noupdate', '-q', url, dest))
         self.run_command(
-            make_command('update', '-q') + rev_options.to_args(),
+            make_command('update', '-q', rev_options.to_args()),
             cwd=dest,
         )
 
@@ -67,13 +67,13 @@ def switch(self, dest, url, rev_options):
                 'Could not switch Mercurial repository to %s: %s', url, exc,
             )
         else:
-            cmd_args = make_command('update', '-q') + rev_options.to_args()
+            cmd_args = make_command('update', '-q', rev_options.to_args())
             self.run_command(cmd_args, cwd=dest)
 
     def update(self, dest, url, rev_options):
         # type: (str, HiddenText, RevOptions) -> None
         self.run_command(['pull', '-q'], cwd=dest)
-        cmd_args = make_command('update', '-q') + rev_options.to_args()
+        cmd_args = make_command('update', '-q', rev_options.to_args())
         self.run_command(cmd_args, cwd=dest)
 
     @classmethod

src/pip/_internal/vcs/subversion.py

@@ -288,9 +288,9 @@ def export(self, location, url):
                 # Subversion doesn't like to check out over an existing
                 # directory --force fixes this, but was only added in svn 1.5
                 rmtree(location)
-            cmd_args = (
-                make_command('export') + self.get_remote_call_options() +
-                rev_options.to_args() + [url, location]
+            cmd_args = make_command(
+                'export', self.get_remote_call_options(),
+                rev_options.to_args(), url, location,
             )
             self.run_command(cmd_args, show_stdout=False)
 
@@ -303,25 +303,25 @@ def fetch_new(self, dest, url, rev_options):
             rev_display,
             display_path(dest),
         )
-        cmd_args = (
-            make_command('checkout', '-q') + self.get_remote_call_options() +
-            rev_options.to_args() + [url, dest]
+        cmd_args = make_command(
+            'checkout', '-q', self.get_remote_call_options(),
+            rev_options.to_args(), url, dest,
         )
         self.run_command(cmd_args)
 
     def switch(self, dest, url, rev_options):
         # type: (str, HiddenText, RevOptions) -> None
-        cmd_args = (
-            make_command('switch') + self.get_remote_call_options() +
-            rev_options.to_args() + [url, dest]
+        cmd_args = make_command(
+            'switch', self.get_remote_call_options(), rev_options.to_args(),
+            url, dest,
         )
         self.run_command(cmd_args)
 
     def update(self, dest, url, rev_options):
         # type: (str, HiddenText, RevOptions) -> None
-        cmd_args = (
-            make_command('update') + self.get_remote_call_options() +
-            rev_options.to_args() + [dest]
+        cmd_args = make_command(
+            'update', self.get_remote_call_options(), rev_options.to_args(),
+            dest,
         )
         self.run_command(cmd_args)