config: expand tilde in ssh key filepaths

Add home directory expansion for SSH key filepaths. This allows the
`signing.key` configuration value to work more universally across both
Linux and macOS without requiring an absolute path.

This moved and renamed the previous `expand_git_path` function to a more
generic location, and the prior use was updated accordingly.

CHANGELOG.md

@@ -17,6 +17,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * The following diff formats now include information about copies and moves:
   `--color-words`, `--summary`
 
+* A tilde (`~`) at the start of the path will now be expanded to the user's home
+  directory when configuring a `signing.key` for SSH commit signing.
+
 ### Fixed bugs
 
 ## [0.20.0] - 2024-08-07

cli/src/cli_util.rs

@@ -73,7 +73,7 @@ use jj_lib::workspace::{
     default_working_copy_factories, LockedWorkspace, WorkingCopyFactories, Workspace,
     WorkspaceLoadError, WorkspaceLoader,
 };
-use jj_lib::{dag_walk, fileset, git, op_heads_store, op_walk, revset};
+use jj_lib::{dag_walk, file_util, fileset, git, op_heads_store, op_walk, revset};
 use once_cell::unsync::OnceCell;
 use tracing::instrument;
 use tracing_chrome::ChromeLayerBuilder;
@@ -806,7 +806,7 @@ impl WorkspaceCommandHelper {
             if let Some(value) = config.string("core.excludesFile") {
                 let path = str::from_utf8(&value)
                     .ok()
-                    .map(crate::git_util::expand_git_path)?;
+                    .map(file_util::expand_home_path)?;
                 // The configured path is usually absolute, but if it's relative,
                 // the "git" command would read the file at the work-tree directory.
                 Some(self.workspace_root().join(path))

cli/src/git_util.rs

@@ -419,13 +419,3 @@ export or their "parent" branches."#,
     }
     Ok(())
 }
-
-/// Expands "~/" to "$HOME/" as Git seems to do for e.g. core.excludesFile.
-pub fn expand_git_path(path_str: &str) -> PathBuf {
-    if let Some(remainder) = path_str.strip_prefix("~/") {
-        if let Ok(home_dir_str) = std::env::var("HOME") {
-            return PathBuf::from(home_dir_str).join(remainder);
-        }
-    }
-    PathBuf::from(path_str)
-}

docs/config.md

@@ -784,7 +784,7 @@ sign-all = true
 backend = "ssh"
 key = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGj+J6N6SO+4P8dOZqfR1oiay2yxhhHnagH52avUqw5h"
 ## You can also use a path instead of embedding the key
-# key = "/home/me/.ssh/id_for_signing.pub"
+# key = "~/.ssh/id_for_signing.pub"
 ```
 
 By default the ssh backend will look for a `ssh-keygen` binary on your path. If you want

lib/src/file_util.rs

@@ -69,6 +69,16 @@ pub fn remove_dir_contents(dirname: &Path) -> Result<(), PathError> {
     Ok(())
 }
 
+/// Expands "~/" to "$HOME/".
+pub fn expand_home_path(path_str: &str) -> PathBuf {
+    if let Some(remainder) = path_str.strip_prefix("~/") {
+        if let Ok(home_dir_str) = std::env::var("HOME") {
+            return PathBuf::from(home_dir_str).join(remainder);
+        }
+    }
+    PathBuf::from(path_str)
+}
+
 /// Turns the given `to` path into relative path starting from the `from` path.
 ///
 /// Both `from` and `to` paths are supposed to be absolute and normalized in the

lib/src/ssh_signing.rs

@@ -81,8 +81,8 @@ fn run_command(command: &mut Command, stdin: &[u8]) -> SshResult<Vec<u8>> {
 fn ensure_key_as_file(key: &str) -> SshResult<Either<PathBuf, tempfile::TempPath>> {
     let is_inlined_ssh_key = key.starts_with("ssh-");
     if !is_inlined_ssh_key {
-        let key_path = Path::new(key);
-        return Ok(either::Left(key_path.to_path_buf()));
+        let key_path = crate::file_util::expand_home_path(key);
+        return Ok(either::Left(key_path));
     }
 
     let mut pub_key_file = tempfile::Builder::new()