diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 238c5eb..01cfb33 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -2,6 +2,7 @@ mod details;
 mod diff;
 mod filters;
 mod git;
+mod location;
 mod settings;
 
 use std::path::PathBuf;
diff --git a/src-tauri/src/location.rs b/src-tauri/src/location.rs
new file mode 100644
index 0000000..46a629d
--- /dev/null
+++ b/src-tauri/src/location.rs
@@ -0,0 +1,133 @@
+//! Where a repository lives: a folder on this machine, or a folder on another machine
+//! reached over ssh.
+
+use std::path::{Path, PathBuf};
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum Location {
+    Local(PathBuf),
+    /// `target` is what is given to ssh, like `host` or `user@host`.
+    Ssh { target: String, path: String },
+}
+
+/// Reads `[user@]host:path` as a remote location. Everything else is local: text where the
+/// part before the first `:` is a single character (a Windows drive like `C:`) or contains
+/// `/` or `\`, and text that is the whole name of a folder that exists inside `cwd`.
+pub fn parse(text: &str, cwd: &Path) -> Location {
+    let local = || Location::Local(PathBuf::from(text));
+    let Some((target, path)) = text.split_once(':') else { return local() };
+    if target.chars().count() <= 1 || target.contains('/') || target.contains('\\') || cwd.join(text).exists() {
+        return local();
+    }
+    Location::Ssh { target: target.to_string(), path: path.to_string() }
+}
+
+impl Location {
+    /// The text the user would type to open this location.
+    pub fn name(&self) -> String {
+        match self {
+            Location::Local(path) => path.to_string_lossy().into_owned(),
+            Location::Ssh { target, path } => format!("{target}:{path}"),
+        }
+    }
+
+    /// The same machine with another folder.
+    pub fn with_path(&self, path: &str) -> Location {
+        match self {
+            Location::Local(_) => Location::Local(PathBuf::from(path)),
+            Location::Ssh { target, .. } => Location::Ssh { target: target.clone(), path: path.to_string() },
+        }
+    }
+}
+
+/// Wraps one word in single quotes so a shell reads it back unchanged.
+pub fn quote(word: &str) -> String {
+    format!("'{}'", word.replace('\'', r"'\''"))
+}
+
+/// The command line to run on the remote machine: `git -C <path>` followed by `args`.
+/// A path starting with `~/` keeps the `~` outside the quotes so the shell still
+/// replaces it with the home folder.
+pub fn remote_command(path: &str, args: &[&str]) -> String {
+    let path = match path.strip_prefix("~/") {
+        Some(rest) => format!("~/{}", quote(rest)),
+        None => quote(path),
+    };
+    let mut command = format!("git -C {path}");
+    for arg in args {
+        command.push(' ');
+        command.push_str(&quote(arg));
+    }
+    command
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::process::Command;
+
+    fn cwd() -> PathBuf {
+        std::env::temp_dir()
+    }
+
+    #[test]
+    fn reads_remote_locations() {
+        assert_eq!(
+            parse("myserver:/srv/app", &cwd()),
+            Location::Ssh { target: "myserver".into(), path: "/srv/app".into() }
+        );
+        assert_eq!(
+            parse("ada@myserver:~/x", &cwd()),
+            Location::Ssh { target: "ada@myserver".into(), path: "~/x".into() }
+        );
+    }
+
+    #[test]
+    fn keeps_local_paths_local() {
+        for text in [r"C:\code\x", "C:/code/x", "./a:b", "relative/dir", "/abs/dir"] {
+            assert_eq!(parse(text, &cwd()), Location::Local(PathBuf::from(text)), "{text}");
+        }
+    }
+
+    #[test]
+    fn keeps_an_existing_local_folder_with_a_colon_local() {
+        let temp = std::env::temp_dir().join(format!("gites-location-{}", std::process::id()));
+        let folder = temp.join("notes:2024");
+        std::fs::create_dir_all(&folder).unwrap();
+        assert_eq!(parse("notes:2024", &temp), Location::Local(PathBuf::from("notes:2024")));
+        std::fs::remove_dir_all(&folder).unwrap();
+        assert_eq!(parse("notes:2024", &temp), Location::Ssh { target: "notes".into(), path: "2024".into() });
+        std::fs::remove_dir_all(&temp).unwrap();
+    }
+
+    #[test]
+    fn names_locations() {
+        let remote = Location::Ssh { target: "myserver".into(), path: "/srv/app".into() };
+        assert_eq!(remote.name(), "myserver:/srv/app");
+        assert_eq!(Location::Local(PathBuf::from("/abs/dir")).name(), "/abs/dir");
+    }
+
+    #[test]
+    fn changes_only_the_path() {
+        let remote = Location::Ssh { target: "ada@myserver".into(), path: "/srv/app".into() };
+        assert_eq!(remote.with_path("/srv/other"), Location::Ssh { target: "ada@myserver".into(), path: "/srv/other".into() });
+        assert_eq!(Location::Local(PathBuf::from("/a")).with_path("/b"), Location::Local(PathBuf::from("/b")));
+    }
+
+    #[test]
+    fn quoted_words_survive_a_shell() {
+        for word in ["plain", "with space", "it's", "\"double\"", "$HOME", "a;b", "*", "line\nbreak"] {
+            let out = Command::new("sh").arg("-c").arg(format!("printf %s {}", quote(word))).output().unwrap();
+            assert_eq!(String::from_utf8(out.stdout).unwrap(), word);
+        }
+    }
+
+    #[test]
+    fn builds_the_remote_command() {
+        assert_eq!(
+            remote_command("/srv/my app", &["log", "--format=%H"]),
+            "git -C '/srv/my app' 'log' '--format=%H'"
+        );
+        assert_eq!(remote_command("~/x y", &["status"]), "git -C ~/'x y' 'status'");
+    }
+}