feat: Support prereleases of micromamba

.github/workflows/test.yml

@@ -44,6 +44,16 @@ jobs:
           micromamba info | grep -q "environment : base"
         shell: bash -el {0}
 
+  micromamba-prerelease-version:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: ./
+        with:
+          micromamba-version: '2.6.0.rc0'
+      - run: test "$(micromamba --version)" = "2.6.0.rc0"
+        shell: bash -el {0}
+
   micromamba-old-version-1:
     runs-on: ubuntu-latest
     steps:

README.md

@@ -33,14 +33,25 @@ To see all available input arguments, see the [`action.yml`](action.yml) file.
 ### Micromamba version
 
 You can specify the version of micromamba to be installed using the `micromamba-version` input.
+If omitted, the action installs the latest **stable** release (prereleases are excluded).
 
 ```yml
 - uses: mamba-org/setup-micromamba@v3
   with:
-    # Any version from https://github.com/mamba-org/micromamba-releases
+    # Any stable version from https://github.com/mamba-org/micromamba-releases
     micromamba-version: '2.0.5-0'
 ```
 
+Prerelease versions (for example `2.6.0.rc0` or `2.6.0.alpha0`) are only installed when
+you set `micromamba-version` explicitly. They are fetched from the
+[`conda-forge/label/micromamba_prerelease`](https://anaconda.org/conda-forge/label/micromamba_prerelease) channel.
+
+```yml
+- uses: mamba-org/setup-micromamba@v3
+  with:
+    micromamba-version: '2.6.0.rc0'
+```
+
 ### Environment creation
 
 `setup-micromamba` allows you to create micromamba environments from an environment file or from a list of packages.

action.yml

@@ -37,7 +37,10 @@ inputs:
   micromamba-version:
     description: |
       Version of micromamba to install.
-      Must match with a micromamba version from the https://github.com/mamba-org/micromamba-releases repository or 'latest'.
+      Defaults to `latest` (latest stable release, excluding prereleases).
+      Stable versions use https://github.com/mamba-org/micromamba-releases (e.g. `2.6.0-0`).
+      Prereleases (e.g. `2.6.0.rc0`, `2.6.0.alpha0`) are installed from the
+      `conda-forge/label/micromamba_prerelease` channel when explicitly specified.
   micromamba-url:
     description: |
       URL to download micromamba from.