prefer the full name of powershell

Author: frostming

docs/html/user_guide.rst

@@ -498,7 +498,7 @@ To setup for fish::
 
 To setup for powershell::
 
-   python -m pip completion --posh | Out-File -Encoding default -Append $PROFILE
+   python -m pip completion --powershell | Out-File -Encoding default -Append $PROFILE
 
 Alternatively, you can use the result of the ``completion`` command directly
 with the eval function of your shell, e.g. by adding the following to your

src/pip/_internal/commands/completion.py

@@ -43,7 +43,7 @@
         end
         complete -fa "(__fish_complete_pip)" -c {prog}
     """,
-    "posh": """
+    "powershell": """
         if ((Test-Path Function:\\TabExpansion) -and -not `
             (Test-Path Function:\\_pip_completeBackup)) {{
             Rename-Item Function:\\TabExpansion _pip_completeBackup
@@ -99,10 +99,10 @@ def add_options(self) -> None:
             help="Emit completion code for fish",
         )
         self.cmd_opts.add_option(
-            "--posh",
+            "--powershell",
             "-p",
             action="store_const",
-            const="posh",
+            const="powershell",
             dest="shell",
             help="Emit completion code for powershell",
         )

tests/functional/test_completion.py

@@ -44,7 +44,7 @@
 compctl -K _pip_completion pip""",
     ),
     (
-        "posh",
+        "powershell",
         """\
 if ((Test-Path Function:\\TabExpansion) -and -not `
     (Test-Path Function:\\_pip_completeBackup)) {
@@ -135,7 +135,8 @@ def test_completion_alone(autocomplete_script):
     """
     result = autocomplete_script.pip("completion", allow_stderr_error=True)
     assert (
-        "ERROR: You must pass --bash or --fish or --posh or --zsh" in result.stderr
+        "ERROR: You must pass --bash or --fish or --powershell or --zsh"
+        in result.stderr
     ), ("completion alone failed -- " + result.stderr)
 
 
@@ -325,7 +326,7 @@ def test_completion_path_after_option(autocomplete, data):
     )
 
 
-@pytest.mark.parametrize("flag", ["--bash", "--zsh", "--fish", "--posh"])
+@pytest.mark.parametrize("flag", ["--bash", "--zsh", "--fish", "--powershell"])
 def test_completion_uses_same_executable_name(
     autocomplete_script, flag, deprecated_python
 ):