Add support for Just task runner

docs/tools.md

@@ -10,6 +10,13 @@ the command will not be exposed, as we assume that this is an internal target.
 A good example of a project using this pattern is
 [podman](https://github.com/containers/podman).
 
+## Justfile
+
+If a [justfile](https://github.com/casey/just/tree/master/examples) is found on
+the repository root, the tool will expose all its targets that have a trailing
+comment with a double hash - `## <description>`. If the comment is not found,
+the command will not be exposed, as we assume that this is an internal target.
+
 ## npm
 
 If a [package.json](https://docs.npmjs.com/cli/v7/configuring-npm/package-json)

pyproject.toml

@@ -50,6 +50,7 @@ mk = "mk.__main__:cli"
 ansible = "mk.tools.ansible:AnsibleTool"
 cmake = "mk.tools.cmake:CMakeTool"
 git = "mk.tools.git:GitTool"
+just = "mk.tools.just:JustTool"
 make = "mk.tools.make:MakeTool"
 node = "mk.tools.node:NodeTool"
 pypackage = "mk.tools.py_package:PyPackageTool"

src/mk/tools/just.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import os
+import re
+from pathlib import Path
+
+from mk.exec import run_or_fail
+from mk.tools import Action, Tool
+
+
+class JustTool(Tool):
+    name = "just"
+
+    def __init__(self) -> None:
+        super().__init__(self)
+        self.justfile: str | None = None
+
+    def run(self, action: Action | None = None) -> None:
+        cmd = ["just"]
+        if action:
+            cmd.append(action.name)
+        run_or_fail(cmd, tee=True)
+
+    def is_present(self, path: Path) -> bool:
+        for name in ["Justfile", "justfile", "JUSTFILE", ".justfile"]:
+            justfile = os.path.join(path, name)
+            if os.path.isfile(justfile):
+                self.justfile = justfile
+                return True
+        return False
+
+    def actions(self) -> list[Action]:
+        actions = []
+        if not self.justfile:
+            msg = "Justfile not found"
+            raise RuntimeError(msg)
+        # pylint: disable=duplicate-code
+        with open(self.justfile, encoding="utf-8") as file:
+            for line in file.readlines():
+                # Current implementation assumes that descriptions are added
+                # using double ## after the target name.
+                # Inspired by https://github.com/containers/podman/blob/master/Makefile#L127
+                match = re.match(r"^([a-zA-Z_-]+):.*?## (.*)$$", line)
+                if match:
+                    target, description = match.groups()
+                    actions.append(
+                        Action(name=target, tool=self, description=description),
+                    )
+        # pylint: enable=duplicate-code
+        return actions