We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
After uprade pip to version 23.3+  cant use hg+http with current branch
### Description

After uprade pip to version 23.3+ can`t isntall my package from repository with current branch
if i use older version or without branch works fine, olready use tag and hash instead of branch

### Expected behavior

pip will work correctly

### pip version

23.3

### Python version

3.9

### OS

Linux

### How to Reproduce

try to install from hg repository using branch or hash
for example 
pip install hg+http://mylink/hg/folder/mypackage@0.1.3

### Output

Collecting hg+http://mylink/hg/folder/mypackage@0.1.3
  Cloning hg  http://mylink/hg/folder/mypackage (to revision 0.1.3) to /tmp/pip-req-build-hmzsjinv
  Running command hg clone --noupdate --quiet http://mylink/hg/folder/mypackage /tmp/pip-req-build-hmzsjinv

  Running command hg update --quiet -r=0.1.3
  hg: parse error at 0: not a prefix: =
  (=0.1.3
   ^ here)
  error: subprocess-exited-with-error
  
  × hg update --quiet -r=0.1.3 did not run successfully.
  │ exit code: 255
  ╰─> See above for output.
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× hg update --quiet -r=0.1.3 did not run successfully.
│ exit code: 255
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.

### Code of Conduct

- [X] I agree to follow the [PSF Code of Conduct](https://www.python.org/psf/conduct/).

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `src/pip/_internal/vcs/mercurial.py`
Content:
```
1 import configparser
2 import logging
3 import os
4 from typing import List, Optional, Tuple
5 
6 from pip._internal.exceptions import BadCommand, InstallationError
7 from pip._internal.utils.misc import HiddenText, display_path
8 from pip._internal.utils.subprocess import make_command
9 from pip._internal.utils.urls import path_to_url
10 from pip._internal.vcs.versioncontrol import (
11     RevOptions,
12     VersionControl,
13     find_path_to_project_root_from_repo_root,
14     vcs,
15 )
16 
17 logger = logging.getLogger(__name__)
18 
19 
20 class Mercurial(VersionControl):
21     name = "hg"
22     dirname = ".hg"
23     repo_name = "clone"
24     schemes = (
25         "hg+file",
26         "hg+http",
27         "hg+https",
28         "hg+ssh",
29         "hg+static-http",
30     )
31 
32     @staticmethod
33     def get_base_rev_args(rev: str) -> List[str]:
34         return [f"-r={rev}"]
35 
36     def fetch_new(
37         self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int
38     ) -> None:
39         rev_display = rev_options.to_display()
40         logger.info(
41             "Cloning hg %s%s to %s",
42             url,
43             rev_display,
44             display_path(dest),
45         )
46         if verbosity <= 0:
47             flags: Tuple[str, ...] = ("--quiet",)
48         elif verbosity == 1:
49             flags = ()
50         elif verbosity == 2:
51             flags = ("--verbose",)
52         else:
53             flags = ("--verbose", "--debug")
54         self.run_command(make_command("clone", "--noupdate", *flags, url, dest))
55         self.run_command(
56             make_command("update", *flags, rev_options.to_args()),
57             cwd=dest,
58         )
59 
60     def switch(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:
61         repo_config = os.path.join(dest, self.dirname, "hgrc")
62         config = configparser.RawConfigParser()
63         try:
64             config.read(repo_config)
65             config.set("paths", "default", url.secret)
66             with open(repo_config, "w") as config_file:
67                 config.write(config_file)
68         except (OSError, configparser.NoSectionError) as exc:
69             logger.warning("Could not switch Mercurial repository to %s: %s", url, exc)
70         else:
71             cmd_args = make_command("update", "-q", rev_options.to_args())
72             self.run_command(cmd_args, cwd=dest)
73 
74     def update(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:
75         self.run_command(["pull", "-q"], cwd=dest)
76         cmd_args = make_command("update", "-q", rev_options.to_args())
77         self.run_command(cmd_args, cwd=dest)
78 
79     @classmethod
80     def get_remote_url(cls, location: str) -> str:
81         url = cls.run_command(
82             ["showconfig", "paths.default"],
83             show_stdout=False,
84             stdout_only=True,
85             cwd=location,
86         ).strip()
87         if cls._is_local_repository(url):
88             url = path_to_url(url)
89         return url.strip()
90 
91     @classmethod
92     def get_revision(cls, location: str) -> str:
93         """
94         Return the repository-local changeset revision number, as an integer.
95         """
96         current_revision = cls.run_command(
97             ["parents", "--template={rev}"],
98             show_stdout=False,
99             stdout_only=True,
100             cwd=location,
101         ).strip()
102         return current_revision
103 
104     @classmethod
105     def get_requirement_revision(cls, location: str) -> str:
106         """
107         Return the changeset identification hash, as a 40-character
108         hexadecimal string
109         """
110         current_rev_hash = cls.run_command(
111             ["parents", "--template={node}"],
112             show_stdout=False,
113             stdout_only=True,
114             cwd=location,
115         ).strip()
116         return current_rev_hash
117 
118     @classmethod
119     def is_commit_id_equal(cls, dest: str, name: Optional[str]) -> bool:
120         """Always assume the versions don't match"""
121         return False
122 
123     @classmethod
124     def get_subdirectory(cls, location: str) -> Optional[str]:
125         """
126         Return the path to Python project root, relative to the repo root.
127         Return None if the project root is in the repo root.
128         """
129         # find the repo root
130         repo_root = cls.run_command(
131             ["root"], show_stdout=False, stdout_only=True, cwd=location
132         ).strip()
133         if not os.path.isabs(repo_root):
134             repo_root = os.path.abspath(os.path.join(location, repo_root))
135         return find_path_to_project_root_from_repo_root(location, repo_root)
136 
137     @classmethod
138     def get_repository_root(cls, location: str) -> Optional[str]:
139         loc = super().get_repository_root(location)
140         if loc:
141             return loc
142         try:
143             r = cls.run_command(
144                 ["root"],
145                 cwd=location,
146                 show_stdout=False,
147                 stdout_only=True,
148                 on_returncode="raise",
149                 log_failed_cmd=False,
150             )
151         except BadCommand:
152             logger.debug(
153                 "could not determine if %s is under hg control "
154                 "because hg is not available",
155                 location,
156             )
157             return None
158         except InstallationError:
159             return None
160         return os.path.normpath(r.rstrip("\r\n"))
161 
162 
163 vcs.register(Mercurial)
164
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py
--- a/src/pip/_internal/vcs/mercurial.py
+++ b/src/pip/_internal/vcs/mercurial.py
@@ -31,7 +31,7 @@
 
     @staticmethod
     def get_base_rev_args(rev: str) -> List[str]:
-        return [f"-r={rev}"]
+        return [f"--rev={rev}"]
 
     def fetch_new(
         self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int

{"golden_diff": "diff --git a/src/pip/_internal/vcs/mercurial.py b/src/pip/_internal/vcs/mercurial.py\n--- a/src/pip/_internal/vcs/mercurial.py\n+++ b/src/pip/_internal/vcs/mercurial.py\n@@ -31,7 +31,7 @@\n \n     @staticmethod\n     def get_base_rev_args(rev: str) -> List[str]:\n-        return [f\"-r={rev}\"]\n+        return [f\"--rev={rev}\"]\n \n     def fetch_new(\n         self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int\n", "issue": "After uprade pip to version 23.3+  cant use hg+http with current branch\n### Description\n\nAfter uprade pip to version 23.3+ can`t isntall my package from repository with current branch\r\nif i use older version or without branch works fine, olready use tag and hash instead of branch\n\n### Expected behavior\n\npip will work correctly\n\n### pip version\n\n23.3\n\n### Python version\n\n3.9\n\n### OS\n\nLinux\n\n### How to Reproduce\n\ntry to install from hg repository using branch or hash\r\nfor example \r\npip install hg+http://mylink/hg/folder/mypackage@0.1.3\n\n### Output\n\nCollecting hg+http://mylink/hg/folder/mypackage@0.1.3\r\n  Cloning hg  http://mylink/hg/folder/mypackage (to revision 0.1.3) to /tmp/pip-req-build-hmzsjinv\r\n  Running command hg clone --noupdate --quiet http://mylink/hg/folder/mypackage /tmp/pip-req-build-hmzsjinv\r\n\r\n  Running command hg update --quiet -r=0.1.3\r\n  hg: parse error at 0: not a prefix: =\r\n  (=0.1.3\r\n   ^ here)\r\n  error: subprocess-exited-with-error\r\n  \r\n  \u00d7 hg update --quiet -r=0.1.3 did not run successfully.\r\n  \u2502 exit code: 255\r\n  \u2570\u2500> See above for output.\r\n  \r\n  note: This error originates from a subprocess, and is likely not a problem with pip.\r\nerror: subprocess-exited-with-error\r\n\r\n\u00d7 hg update --quiet -r=0.1.3 did not run successfully.\r\n\u2502 exit code: 255\r\n\u2570\u2500> See above for output.\r\n\r\nnote: This error originates from a subprocess, and is likely not a problem with pip.\n\n### Code of Conduct\n\n- [X] I agree to follow the [PSF Code of Conduct](https://www.python.org/psf/conduct/).\n", "before_files": [{"content": "import configparser\nimport logging\nimport os\nfrom typing import List, Optional, Tuple\n\nfrom pip._internal.exceptions import BadCommand, InstallationError\nfrom pip._internal.utils.misc import HiddenText, display_path\nfrom pip._internal.utils.subprocess import make_command\nfrom pip._internal.utils.urls import path_to_url\nfrom pip._internal.vcs.versioncontrol import (\n    RevOptions,\n    VersionControl,\n    find_path_to_project_root_from_repo_root,\n    vcs,\n)\n\nlogger = logging.getLogger(__name__)\n\n\nclass Mercurial(VersionControl):\n    name = \"hg\"\n    dirname = \".hg\"\n    repo_name = \"clone\"\n    schemes = (\n        \"hg+file\",\n        \"hg+http\",\n        \"hg+https\",\n        \"hg+ssh\",\n        \"hg+static-http\",\n    )\n\n    @staticmethod\n    def get_base_rev_args(rev: str) -> List[str]:\n        return [f\"-r={rev}\"]\n\n    def fetch_new(\n        self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int\n    ) -> None:\n        rev_display = rev_options.to_display()\n        logger.info(\n            \"Cloning hg %s%s to %s\",\n            url,\n            rev_display,\n            display_path(dest),\n        )\n        if verbosity <= 0:\n            flags: Tuple[str, ...] = (\"--quiet\",)\n        elif verbosity == 1:\n            flags = ()\n        elif verbosity == 2:\n            flags = (\"--verbose\",)\n        else:\n            flags = (\"--verbose\", \"--debug\")\n        self.run_command(make_command(\"clone\", \"--noupdate\", *flags, url, dest))\n        self.run_command(\n            make_command(\"update\", *flags, rev_options.to_args()),\n            cwd=dest,\n        )\n\n    def switch(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:\n        repo_config = os.path.join(dest, self.dirname, \"hgrc\")\n        config = configparser.RawConfigParser()\n        try:\n            config.read(repo_config)\n            config.set(\"paths\", \"default\", url.secret)\n            with open(repo_config, \"w\") as config_file:\n                config.write(config_file)\n        except (OSError, configparser.NoSectionError) as exc:\n            logger.warning(\"Could not switch Mercurial repository to %s: %s\", url, exc)\n        else:\n            cmd_args = make_command(\"update\", \"-q\", rev_options.to_args())\n            self.run_command(cmd_args, cwd=dest)\n\n    def update(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:\n        self.run_command([\"pull\", \"-q\"], cwd=dest)\n        cmd_args = make_command(\"update\", \"-q\", rev_options.to_args())\n        self.run_command(cmd_args, cwd=dest)\n\n    @classmethod\n    def get_remote_url(cls, location: str) -> str:\n        url = cls.run_command(\n            [\"showconfig\", \"paths.default\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        if cls._is_local_repository(url):\n            url = path_to_url(url)\n        return url.strip()\n\n    @classmethod\n    def get_revision(cls, location: str) -> str:\n        \"\"\"\n        Return the repository-local changeset revision number, as an integer.\n        \"\"\"\n        current_revision = cls.run_command(\n            [\"parents\", \"--template={rev}\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        return current_revision\n\n    @classmethod\n    def get_requirement_revision(cls, location: str) -> str:\n        \"\"\"\n        Return the changeset identification hash, as a 40-character\n        hexadecimal string\n        \"\"\"\n        current_rev_hash = cls.run_command(\n            [\"parents\", \"--template={node}\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        return current_rev_hash\n\n    @classmethod\n    def is_commit_id_equal(cls, dest: str, name: Optional[str]) -> bool:\n        \"\"\"Always assume the versions don't match\"\"\"\n        return False\n\n    @classmethod\n    def get_subdirectory(cls, location: str) -> Optional[str]:\n        \"\"\"\n        Return the path to Python project root, relative to the repo root.\n        Return None if the project root is in the repo root.\n        \"\"\"\n        # find the repo root\n        repo_root = cls.run_command(\n            [\"root\"], show_stdout=False, stdout_only=True, cwd=location\n        ).strip()\n        if not os.path.isabs(repo_root):\n            repo_root = os.path.abspath(os.path.join(location, repo_root))\n        return find_path_to_project_root_from_repo_root(location, repo_root)\n\n    @classmethod\n    def get_repository_root(cls, location: str) -> Optional[str]:\n        loc = super().get_repository_root(location)\n        if loc:\n            return loc\n        try:\n            r = cls.run_command(\n                [\"root\"],\n                cwd=location,\n                show_stdout=False,\n                stdout_only=True,\n                on_returncode=\"raise\",\n                log_failed_cmd=False,\n            )\n        except BadCommand:\n            logger.debug(\n                \"could not determine if %s is under hg control \"\n                \"because hg is not available\",\n                location,\n            )\n            return None\n        except InstallationError:\n            return None\n        return os.path.normpath(r.rstrip(\"\\r\\n\"))\n\n\nvcs.register(Mercurial)\n", "path": "src/pip/_internal/vcs/mercurial.py"}], "after_files": [{"content": "import configparser\nimport logging\nimport os\nfrom typing import List, Optional, Tuple\n\nfrom pip._internal.exceptions import BadCommand, InstallationError\nfrom pip._internal.utils.misc import HiddenText, display_path\nfrom pip._internal.utils.subprocess import make_command\nfrom pip._internal.utils.urls import path_to_url\nfrom pip._internal.vcs.versioncontrol import (\n    RevOptions,\n    VersionControl,\n    find_path_to_project_root_from_repo_root,\n    vcs,\n)\n\nlogger = logging.getLogger(__name__)\n\n\nclass Mercurial(VersionControl):\n    name = \"hg\"\n    dirname = \".hg\"\n    repo_name = \"clone\"\n    schemes = (\n        \"hg+file\",\n        \"hg+http\",\n        \"hg+https\",\n        \"hg+ssh\",\n        \"hg+static-http\",\n    )\n\n    @staticmethod\n    def get_base_rev_args(rev: str) -> List[str]:\n        return [f\"--rev={rev}\"]\n\n    def fetch_new(\n        self, dest: str, url: HiddenText, rev_options: RevOptions, verbosity: int\n    ) -> None:\n        rev_display = rev_options.to_display()\n        logger.info(\n            \"Cloning hg %s%s to %s\",\n            url,\n            rev_display,\n            display_path(dest),\n        )\n        if verbosity <= 0:\n            flags: Tuple[str, ...] = (\"--quiet\",)\n        elif verbosity == 1:\n            flags = ()\n        elif verbosity == 2:\n            flags = (\"--verbose\",)\n        else:\n            flags = (\"--verbose\", \"--debug\")\n        self.run_command(make_command(\"clone\", \"--noupdate\", *flags, url, dest))\n        self.run_command(\n            make_command(\"update\", *flags, rev_options.to_args()),\n            cwd=dest,\n        )\n\n    def switch(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:\n        repo_config = os.path.join(dest, self.dirname, \"hgrc\")\n        config = configparser.RawConfigParser()\n        try:\n            config.read(repo_config)\n            config.set(\"paths\", \"default\", url.secret)\n            with open(repo_config, \"w\") as config_file:\n                config.write(config_file)\n        except (OSError, configparser.NoSectionError) as exc:\n            logger.warning(\"Could not switch Mercurial repository to %s: %s\", url, exc)\n        else:\n            cmd_args = make_command(\"update\", \"-q\", rev_options.to_args())\n            self.run_command(cmd_args, cwd=dest)\n\n    def update(self, dest: str, url: HiddenText, rev_options: RevOptions) -> None:\n        self.run_command([\"pull\", \"-q\"], cwd=dest)\n        cmd_args = make_command(\"update\", \"-q\", rev_options.to_args())\n        self.run_command(cmd_args, cwd=dest)\n\n    @classmethod\n    def get_remote_url(cls, location: str) -> str:\n        url = cls.run_command(\n            [\"showconfig\", \"paths.default\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        if cls._is_local_repository(url):\n            url = path_to_url(url)\n        return url.strip()\n\n    @classmethod\n    def get_revision(cls, location: str) -> str:\n        \"\"\"\n        Return the repository-local changeset revision number, as an integer.\n        \"\"\"\n        current_revision = cls.run_command(\n            [\"parents\", \"--template={rev}\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        return current_revision\n\n    @classmethod\n    def get_requirement_revision(cls, location: str) -> str:\n        \"\"\"\n        Return the changeset identification hash, as a 40-character\n        hexadecimal string\n        \"\"\"\n        current_rev_hash = cls.run_command(\n            [\"parents\", \"--template={node}\"],\n            show_stdout=False,\n            stdout_only=True,\n            cwd=location,\n        ).strip()\n        return current_rev_hash\n\n    @classmethod\n    def is_commit_id_equal(cls, dest: str, name: Optional[str]) -> bool:\n        \"\"\"Always assume the versions don't match\"\"\"\n        return False\n\n    @classmethod\n    def get_subdirectory(cls, location: str) -> Optional[str]:\n        \"\"\"\n        Return the path to Python project root, relative to the repo root.\n        Return None if the project root is in the repo root.\n        \"\"\"\n        # find the repo root\n        repo_root = cls.run_command(\n            [\"root\"], show_stdout=False, stdout_only=True, cwd=location\n        ).strip()\n        if not os.path.isabs(repo_root):\n            repo_root = os.path.abspath(os.path.join(location, repo_root))\n        return find_path_to_project_root_from_repo_root(location, repo_root)\n\n    @classmethod\n    def get_repository_root(cls, location: str) -> Optional[str]:\n        loc = super().get_repository_root(location)\n        if loc:\n            return loc\n        try:\n            r = cls.run_command(\n                [\"root\"],\n                cwd=location,\n                show_stdout=False,\n                stdout_only=True,\n                on_returncode=\"raise\",\n                log_failed_cmd=False,\n            )\n        except BadCommand:\n            logger.debug(\n                \"could not determine if %s is under hg control \"\n                \"because hg is not available\",\n                location,\n            )\n            return None\n        except InstallationError:\n            return None\n        return os.path.normpath(r.rstrip(\"\\r\\n\"))\n\n\nvcs.register(Mercurial)\n", "path": "src/pip/_internal/vcs/mercurial.py"}]}