Remove dependency on files for running compare.

The tests still use files since they get the test name from a file but compare does the same action via stdin so it can operator on any org source.

src/compare/parse.rs

@@ -1,22 +1,22 @@
-use std::path::Path;
 use std::process::Command;
 
-pub fn emacs_parse_org_document<'a, C>(file_path: C) -> Result<String, Box<dyn std::error::Error>>
+pub fn emacs_parse_org_document<C>(file_contents: C) -> Result<String, Box<dyn std::error::Error>>
 where
-    C: AsRef<Path>,
+    C: AsRef<str>,
 {
-    let elisp_script = r#"(progn
+    let escaped_file_contents = escape_elisp_string(file_contents);
+    let elisp_script = format!(r#"(progn
+     (erase-buffer)
+     (insert "{escaped_file_contents}")
      (org-mode)
      (message "%s" (pp-to-string (org-element-parse-buffer)))
-)"#;
+)"#, escaped_file_contents=escaped_file_contents);
     let mut cmd = Command::new("emacs");
     let proc = cmd
         .arg("-q")
         .arg("--no-site-file")
         .arg("--no-splash")
         .arg("--batch")
-        .arg("--insert")
-        .arg(file_path.as_ref().as_os_str())
         .arg("--eval")
         .arg(elisp_script);
     let out = proc.output()?;
@@ -24,3 +24,25 @@ where
     let org_sexp = out.stderr;
     Ok(String::from_utf8(org_sexp)?)
 }
+
+fn escape_elisp_string<C>(file_contents: C) -> String
+where
+    C: AsRef<str>,
+{
+    let source = file_contents.as_ref();
+    let source_len = source.len();
+    // We allocate a string 10% larger than the source to account for escape characters. Without this, we would have more allocations during processing.
+    let mut output = String::with_capacity(source_len + (source_len / 10));
+    for c in source.chars() {
+        match c {
+            '"' | '\\' => {
+                output.push('\\');
+                output.push(c);
+            }
+            _ => {
+                output.push(c);
+            }
+        }
+    }
+    output
+}