add README and License

License

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+Copyright 2024 National Center for Atmospheric Sciences (NCAR)
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+“Software”), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# git-fleximod
+
+Flexible Submodule Management for Git
+
+## Overview
+
+Git-fleximod is a Python-based tool that extends Git's submodule capabilities, offering additional features for managing submodules in a more flexible and efficient way.
+
+## Installation
+
+    Install using pip:
+        pip install git-fleximod
+
+## Usage
+
+    Basic Usage:
+        git fleximod <command> [options]
+    Available Commands:
+        install: Install submodules according to configuration.
+        status: Display the status of submodules.
+        update: Update submodules to their latest commits.
+    Additional Options:
+        See git fleximod --help for more details.
+
+## Supported .gitmodules Variables
+
+    fxtag: Specify a specific tag or branch to checkout for a submodule.
+    fxrequired: Mark a submodule's checkout behavior, with allowed values:
+      - T:T: Top-level and required (checked out only when this is the Toplevel module).
+      - T:F: Top-level and optional (checked out with --optional flag if this is the Toplevel module).
+      - I:T: Internal and required (always checked out).
+      - I:F: Internal and optional (checked out with --optional flag).
+    fxsparse: Enable sparse checkout for a submodule, pointing to a file containing sparse checkout paths.
+
+## Sparse Checkouts
+
+    To enable sparse checkout for a submodule, set the fxsparse variable
+    in the .gitmodules file to the path of a file containing the desired
+    sparse checkout paths. Git-fleximod will automatically configure
+    sparse checkout based on this file when applicable commands are run.
+
+## Examples
+
+    Installing submodules with optional ones: git fleximod install --optional
+    Checking out a specific tag for a submodule: git fleximod update --fxtag=v1.2.3 submodule-name
+
+## Contributing
+
+We welcome contributions! Please see the CONTRIBUTING.md file for guidelines.
+
+## License
+
+Git-fleximod is released under the MIT License.