Convert creates tempdir in parent of destination

`git prole convert` now creates a tempdir in the parent of the
determined destination of the converted repo.
This prevents some errors when the /tmp directory is on a different
filesystem, such as a tmpfs.

The tempdir will be deleted if and only if it is empty after conversion.
This should always be the case and is to prevent any data loss.

Fixes issue #96

src/convert.rs

@@ -211,7 +211,6 @@ where
         //     suffix removed
         //   - Otherwise just use the git dir path.
 
-        let tempdir = Utf8TempDir::new()?.into_path();
         // Tests:
         // - `convert_from_bare`
         // - `convert_bare_dot_git`
@@ -227,8 +226,14 @@ where
         let destination_name = destination
             .file_name()
             .ok_or_else(|| miette!("Destination has no basename: {destination}"))?;
+        let destination_parent = destination
+            .parent()
+            .ok_or_else(|| miette!("Destination has no parent: {destination}"))?
+            .to_path_buf();
         tracing::debug!(%destination, "Destination determined");
 
+        let tempdir = Utf8TempDir::new(&destination_parent)?.into_path();
+
         let default_branch = match opts.default_branch {
             // Tests:
             // - `convert_explicit_default_branch`
@@ -553,6 +558,17 @@ where
         );
         tracing::info!("You may need to `cd .` to refresh your shell");
 
+        // Make sure to delete the tempdir if it's empty
+        match fs_err::read_dir(&self.tempdir) {
+            Ok(rd) => {
+                if rd.count() == 1 {
+                    tracing::info!("Temporary directory isn't empty: {0}", self.tempdir)
+                }
+            }
+            Err(err) => miette::bail!(err),
+        };
+        fs::remove_dir(&self.tempdir)?;
+
         Ok(())
     }
 

src/utf8tempdir.rs

@@ -14,8 +14,8 @@ pub struct Utf8TempDir {
 }
 
 impl Utf8TempDir {
-    pub fn new() -> miette::Result<Self> {
-        let inner = tempfile::tempdir().into_diagnostic()?;
+    pub fn new(parent_dir: &Utf8PathBuf) -> miette::Result<Self> {
+        let inner = tempfile::tempdir_in(parent_dir).into_diagnostic()?;
         let path = inner.path().to_owned().try_into().into_diagnostic()?;
         Ok(Self {
             inner: Some(inner),

test-harness/src/lib.rs

@@ -29,7 +29,7 @@ pub struct GitProle {
 
 impl GitProle {
     pub fn new() -> miette::Result<Self> {
-        let mut tempdir = Utf8TempDir::new()?;
+        let mut tempdir = Utf8TempDir::new(&Utf8PathBuf::from("./"))?;
 
         if std::env::var("KEEP_TEMP").is_ok() {
             tempdir.persist();