chore: remove unnecessary result on join_unix_path (#7506)

### Description

Realized that this shouldn't ever fail unless we bypass the checks done
in the constructors for both `AbsoluteSystemPath` and
`RelativeUnixPath`. The only failure point is converting the `PathBuf`
to `AbsoluteSystemPathBuf` which itself has [two failure
points](https://github.com/vercel/turbo/blob/main/crates/turborepo-paths/src/absolute_system_path_buf.rs#L208).
- Conversion from stdlib `PathBuf` to `Utf8PathBuf` which only fails if
the [path can't be represented in
utf8](https://docs.rs/camino/latest/src/camino/lib.rs.html#156)
- `AbsoluteSystemPathBuf` constructor which only fails if the input path
isn't absolute

### Testing Instructions

Existing test suite, my reasoning above

Closes TURBO-2428

crates/turborepo-lib/src/globwatcher/mod.rs

@@ -394,15 +394,12 @@ mod test {
 
         for dir in directories.iter() {
             let dir = RelativeUnixPathBuf::new(*dir).unwrap();
-            tmp.join_unix_path(&dir).unwrap().create_dir_all().unwrap();
+            tmp.join_unix_path(&dir).create_dir_all().unwrap();
         }
 
         for file in files.iter() {
             let file = RelativeUnixPathBuf::new(*file).unwrap();
-            tmp.join_unix_path(&file)
-                .unwrap()
-                .create_with_contents("")
-                .unwrap();
+            tmp.join_unix_path(&file).create_with_contents("").unwrap();
         }
     }
 

crates/turborepo-lib/src/run/scope/filter.rs

@@ -676,12 +676,9 @@ mod test {
             .map(|package_path| {
                 let (_, name) = get_name(package_path);
                 (
-                    turbo_root
-                        .join_unix_path(
-                            RelativeUnixPathBuf::new(format!("{package_path}/package.json"))
-                                .unwrap(),
-                        )
-                        .unwrap(),
+                    turbo_root.join_unix_path(
+                        RelativeUnixPathBuf::new(format!("{package_path}/package.json")).unwrap(),
+                    ),
                     PackageJson {
                         name: Some(name.to_string()),
                         dependencies: dependencies.get(name).map(|v| {

crates/turborepo-paths/src/absolute_system_path.rs

@@ -232,14 +232,20 @@ impl AbsoluteSystemPath {
         self.0.as_str()
     }
 
-    pub fn join_unix_path(
-        &self,
-        unix_path: impl AsRef<RelativeUnixPath>,
-    ) -> Result<AbsoluteSystemPathBuf, PathError> {
+    pub fn join_unix_path(&self, unix_path: impl AsRef<RelativeUnixPath>) -> AbsoluteSystemPathBuf {
         let tail = unix_path.as_ref().to_system_path_buf();
-        Ok(AbsoluteSystemPathBuf(
-            self.0.join(tail).as_std_path().clean().try_into()?,
-        ))
+        AbsoluteSystemPathBuf(
+            self.0
+                .join(tail)
+                .as_std_path()
+                .clean()
+                // The unwrap here should never panic as `try_into` will only panic if
+                // - path isn't absolute: self is already absolute, appending to it won't change
+                //   that
+                // - path isn't valid utf8: self and unix_path are both utf8 already
+                .try_into()
+                .expect("joined path is absolute and valid utf8"),
+        )
     }
 
     pub fn anchor(&self, path: &AbsoluteSystemPath) -> Result<AnchoredSystemPathBuf, PathError> {

crates/turborepo-paths/src/absolute_system_path_buf.rs

@@ -269,8 +269,7 @@ mod tests {
         assert_eq!(
             AbsoluteSystemPathBuf::new("/some/dir")
                 .unwrap()
-                .join_unix_path(tail)
-                .unwrap(),
+                .join_unix_path(tail),
             AbsoluteSystemPathBuf::new("/some/other").unwrap(),
         );
     }
@@ -297,8 +296,7 @@ mod tests {
         assert_eq!(
             AbsoluteSystemPathBuf::new("C:\\some\\dir")
                 .unwrap()
-                .join_unix_path(&tail)
-                .unwrap(),
+                .join_unix_path(&tail),
             AbsoluteSystemPathBuf::new("C:\\some\\other").unwrap(),
         );
     }

crates/turborepo-repository/src/package_graph/builder.rs

@@ -640,7 +640,7 @@ impl<'a> DependencyVersion<'a> {
             Some("file") | Some("link") => {
                 // Default to internal if we have the package but somehow cannot get the path
                 RelativeUnixPathBuf::new(self.version)
-                    .and_then(|file_path| cwd.join_unix_path(file_path))
+                    .map(|file_path| cwd.join_unix_path(file_path))
                     .map_or(true, |dep_path| root.contains(&dep_path))
             }
             Some(_) if self.is_external() => {

crates/turborepo-scm/src/git.rs

@@ -167,7 +167,7 @@ impl Git {
         turbo_root: &AbsoluteSystemPath,
         path: &RelativeUnixPath,
     ) -> Result<AnchoredSystemPathBuf, Error> {
-        let absolute_file_path = self.root.join_unix_path(path)?;
+        let absolute_file_path = self.root.join_unix_path(path);
         let anchored_to_turbo_root_file_path = turbo_root.anchor(&absolute_file_path)?;
         Ok(anchored_to_turbo_root_file_path)
     }

crates/turborepo-scm/src/hash_object.rs

@@ -15,7 +15,7 @@ pub(crate) fn hash_objects(
         let span = tracing::info_span!(parent: &parent, "hash_object", ?filename);
         let _enter = span.enter();
 
-        let full_file_path = git_root.join_unix_path(filename)?;
+        let full_file_path = git_root.join_unix_path(filename);
         match git2::Oid::hash_file(git2::ObjectType::Blob, &full_file_path) {
             Ok(hash) => {
                 let package_relative_path =

crates/turborepo-scm/src/lib.rs

@@ -192,7 +192,7 @@ fn find_git_root(turbo_root: &AbsoluteSystemPath) -> Result<AbsoluteSystemPathBu
     if let Some(line) = lines.next() {
         let line = String::from_utf8(line?)?;
         let tail = RelativeUnixPathBuf::new(line)?;
-        turbo_root.join_unix_path(tail).map_err(|e| e.into())
+        Ok(turbo_root.join_unix_path(tail))
     } else {
         let stderr = String::from_utf8_lossy(&rev_parse.stderr);
         Err(Error::git_error(format!(

crates/turborepo-scm/src/manual.rs

@@ -395,7 +395,7 @@ mod tests {
         let mut expected = GitHashes::new();
         for (raw_unix_path, contents, expected_hash) in file_hash.iter() {
             let unix_path = RelativeUnixPath::new(raw_unix_path).unwrap();
-            let file_path = turbo_root.join_unix_path(unix_path).unwrap();
+            let file_path = turbo_root.join_unix_path(unix_path);
             file_path.ensure_dir().unwrap();
             file_path.create_with_contents(contents).unwrap();
             if let Some(hash) = expected_hash {
@@ -427,7 +427,7 @@ mod tests {
         expected = GitHashes::new();
         for (raw_unix_path, contents, expected_hash) in file_hash.iter() {
             let unix_path = RelativeUnixPath::new(raw_unix_path).unwrap();
-            let file_path = turbo_root.join_unix_path(unix_path).unwrap();
+            let file_path = turbo_root.join_unix_path(unix_path);
             file_path.ensure_dir().unwrap();
             file_path.create_with_contents(contents).unwrap();
             if let Some(hash) = expected_hash {