Update CLI help text for shell command and subcommands

Co-authored-by: jjerphan <13029839+jjerphan@users.noreply.github.com>

docs/source/user_guide/micromamba.rst

@@ -21,3 +21,100 @@ It can be used with a drop-in installation without further steps:
 
     /path/to/micromamba create -p /tmp/env 'pytest>=8.0'
     /path/to/micromamba run -p /tmp/env pytest myproject/tests
+
+Shell Command
+=============
+
+The ``micromamba shell`` command provides functionality for launching shells and managing shell initialization scripts for environment activation.
+
+Launching a Shell
+-----------------
+
+When used without subcommands, ``micromamba shell`` launches a new shell session in the specified environment:
+
+.. code-block:: shell
+
+    # Launch a shell in the specified environment
+    micromamba shell -p /path/to/env
+    micromamba shell -n myenv
+
+This is particularly useful in CI/CD environments and Docker containers where you need to work within a specific environment.
+
+Shell Initialization Management
+-------------------------------
+
+The ``micromamba shell`` command also includes several subcommands for managing shell initialization scripts:
+
+``micromamba shell init``
+    Add micromamba initialization scripts to your shell's configuration files (e.g., ``.bashrc``, ``.zshrc``).
+
+``micromamba shell deinit``
+    Remove micromamba initialization scripts from your shell's configuration files.
+
+``micromamba shell reinit``
+    Restore micromamba initialization scripts in your shell's configuration files.
+
+Environment Activation Scripts
+------------------------------
+
+These subcommands generate shell-specific activation code that can be used in scripts or sourced directly:
+
+``micromamba shell activate``
+    Generate activation code for the specified environment.
+
+``micromamba shell deactivate``
+    Generate deactivation code to leave the current environment.
+
+``micromamba shell reactivate``
+    Generate reactivation code to refresh the current environment.
+
+``micromamba shell hook``
+    Generate shell hook scripts for environment activation.
+
+.. code-block:: shell
+
+    # Generate activation code for bash
+    micromamba shell activate -p /path/to/env -s bash
+    
+    # Generate deactivation code
+    micromamba shell deactivate -s bash
+    
+    # Use in a script
+    eval "$(micromamba shell activate -p /path/to/env -s bash)"
+
+Supported Shells
+----------------
+
+The shell command supports the following shells:
+
+* ``bash`` - Bash shell
+* ``zsh`` - Z shell  
+* ``fish`` - Fish shell
+* ``powershell`` - PowerShell
+* ``cmd.exe`` - Windows Command Prompt
+* ``xonsh`` - Xonsh shell
+* ``tcsh`` - Tcsh shell
+* ``dash`` - Dash shell
+* ``nu`` - Nu shell
+* ``posix`` - POSIX-compliant shells
+
+Common Options
+--------------
+
+``-s, --shell SHELL``
+    Specify the shell type. If not provided, micromamba will attempt to detect your shell automatically.
+
+``-p, --prefix PATH``
+    Specify the environment by its installation path.
+
+``-n, --name NAME``
+    Specify the environment by its name.
+
+``-r, --root-prefix PATH``
+    Specify the root prefix (base environment location).
+
+Platform-Specific Features
+---------------------------
+
+``micromamba shell enable_long_path_support``
+    On Windows, this command enables long path support, which allows working with file paths longer than 260 characters.

micromamba/src/shell.cpp

@@ -396,7 +396,7 @@ set_shell_command(CLI::App* shell_subcmd, Configuration& config)
     );
     set_shell_reinit_command(reinit_subsubcmd, config);
 
-    auto* hook_subsubcmd = shell_subcmd->add_subcommand("hook", "Micromamba hook scripts ");
+    auto* hook_subsubcmd = shell_subcmd->add_subcommand("hook", "Output shell hook scripts for environment activation");
     set_shell_hook_command(hook_subsubcmd, config);
 
     auto* acti_subsubcmd = shell_subcmd->add_subcommand(
@@ -419,7 +419,7 @@ set_shell_command(CLI::App* shell_subcmd, Configuration& config)
 
     auto* long_path_subsubcmd = shell_subcmd->add_subcommand(
         "enable_long_path_support",
-        "Output deactivation code for the given shell"
+        "Enable long path support on Windows"
     );
     set_shell_long_path_command(long_path_subsubcmd, config);
 

micromamba/src/umamba.cpp

@@ -39,7 +39,7 @@ set_umamba_command(CLI::App* com, mamba::Configuration& config)
 
     com->add_flag_function("--version", print_version);
 
-    CLI::App* shell_subcom = com->add_subcommand("shell", "Generate shell init scripts");
+    CLI::App* shell_subcom = com->add_subcommand("shell", "Launch a shell or manage shell initialization scripts");
     set_shell_command(shell_subcom, config);
 
     CLI::App* create_subcom = com->add_subcommand("create", "Create new environment");