context: add context

pkh context allows to manage contexts (local, ssh) and run contextualized commands (deb)

in other words, this allows building binary packages over ssh

src/context/local.rs

@@ -0,0 +1,45 @@
+use super::api::{CommandRunner, ContextDriver};
+/// Local context: execute commands locally
+/// Context driver: Does nothing
+/// Command runner: Wrapper around 'std::process::Command'
+use std::io;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+pub struct LocalDriver;
+
+impl ContextDriver for LocalDriver {
+    fn ensure_available(&self, src: &Path, _dest_root: &str) -> io::Result<PathBuf> {
+        src.canonicalize()
+    }
+
+    fn create_runner(&self, program: String) -> Box<dyn CommandRunner> {
+        Box::new(LocalRunner {
+            program,
+            args: Vec::new(),
+        })
+    }
+
+    fn prepare_work_dir(&self) -> io::Result<String> {
+        Ok(".".to_string())
+    }
+}
+
+pub struct LocalRunner {
+    pub program: String,
+    pub args: Vec<String>,
+}
+
+impl CommandRunner for LocalRunner {
+    fn add_arg(&mut self, arg: String) {
+        self.args.push(arg);
+    }
+
+    fn status(&mut self) -> io::Result<std::process::ExitStatus> {
+        Command::new(&self.program).args(&self.args).status()
+    }
+
+    fn output(&mut self) -> io::Result<std::process::Output> {
+        Command::new(&self.program).args(&self.args).output()
+    }
+}