hyperlink: rejigger how hyperlinks work

This essentially takes the work done in #2483 and does a bit of a
facelift. A brief summary:

* We reduce the hyperlink API we expose to just the format, a
  configuration and an environment.
* We move buffer management into a hyperlink-specific interpolator.
* We expand the documentation on --hyperlink-format.
* We rewrite the hyperlink format parser to be a simple state machine
  with support for escaping '{{' and '}}'.
* We remove the 'gethostname' dependency and instead insist on the
  caller to provide the hostname. (So grep-printer doesn't get it
  itself, but the application will.) Similarly for the WSL prefix.
* Probably some other things.

Overall, the general structure of #2483 was kept. The biggest change is
probably requiring the caller to pass in things like a hostname instead
of having the crate do it. I did this for a couple reasons:

1. I feel uncomfortable with code deep inside the printing logic
   reaching out into the environment to assume responsibility for
   retrieving the hostname. This feels more like an application-level
   responsibility. Arguably, path canonicalization falls into this same
   bucket, but it is more difficult to rip that out. (And we can do it
   in the future in a backwards compatible fashion I think.)
2. I wanted to permit end users to tell ripgrep about their system's
   hostname in their own way, e.g., by running a custom executable. I
   want this because I know at least for my own use cases, I sometimes
   log into systems using an SSH hostname that is distinct from the
   system's actual hostname (usually because the system is shared in
   some way or changing its hostname is not allowed/practical).

I think that's about it.

Closes #665, Closes #2483

crates/printer/src/path.rs

@@ -4,7 +4,7 @@ use termcolor::WriteColor;
 
 use crate::{
     color::ColorSpecs,
-    hyperlink::{HyperlinkPattern, HyperlinkSpan},
+    hyperlink::{self, HyperlinkConfig},
     util::PrinterPath,
 };
 
@@ -12,7 +12,7 @@ use crate::{
 #[derive(Clone, Debug)]
 struct Config {
     colors: ColorSpecs,
-    hyperlink_pattern: HyperlinkPattern,
+    hyperlink: HyperlinkConfig,
     separator: Option<u8>,
     terminator: u8,
 }
@@ -21,7 +21,7 @@ impl Default for Config {
     fn default() -> Config {
         Config {
             colors: ColorSpecs::default(),
-            hyperlink_pattern: HyperlinkPattern::default(),
+            hyperlink: HyperlinkConfig::default(),
             separator: None,
             terminator: b'\n',
         }
@@ -43,7 +43,9 @@ impl PathPrinterBuilder {
     /// Create a new path printer with the current configuration that writes
     /// paths to the given writer.
     pub fn build<W: WriteColor>(&self, wtr: W) -> PathPrinter<W> {
-        PathPrinter { config: self.config.clone(), wtr, buf: vec![] }
+        let interpolator =
+            hyperlink::Interpolator::new(&self.config.hyperlink);
+        PathPrinter { config: self.config.clone(), wtr, interpolator }
     }
 
     /// Set the user color specifications to use for coloring in this printer.
@@ -73,7 +75,7 @@ impl PathPrinterBuilder {
         self
     }
 
-    /// Set the hyperlink pattern to use for hyperlinks output by this printer.
+    /// Set the configuration to use for hyperlinks output by this printer.
     ///
     /// Regardless of the hyperlink format provided here, whether hyperlinks
     /// are actually used or not is determined by the implementation of
@@ -83,12 +85,12 @@ impl PathPrinterBuilder {
     ///
     /// This completely overrides any previous hyperlink format.
     ///
-    /// The default pattern format results in not emitting any hyperlinks.
-    pub fn hyperlink_pattern(
+    /// The default configuration results in not emitting any hyperlinks.
+    pub fn hyperlink(
         &mut self,
-        pattern: HyperlinkPattern,
+        config: HyperlinkConfig,
     ) -> &mut PathPrinterBuilder {
-        self.config.hyperlink_pattern = pattern;
+        self.config.hyperlink = config;
         self
     }
 
@@ -140,40 +142,35 @@ impl PathPrinterBuilder {
 pub struct PathPrinter<W> {
     config: Config,
     wtr: W,
-    buf: Vec<u8>,
+    interpolator: hyperlink::Interpolator,
 }
 
 impl<W: WriteColor> PathPrinter<W> {
     /// Write the given path to the underlying writer.
     pub fn write(&mut self, path: &Path) -> io::Result<()> {
-        let ppath = PrinterPath::with_separator(path, self.config.separator);
+        let ppath = PrinterPath::new(path.as_ref())
+            .with_separator(self.config.separator);
         if !self.wtr.supports_color() {
             self.wtr.write_all(ppath.as_bytes())?;
         } else {
-            let mut hyperlink = self.start_hyperlink_span(&ppath)?;
+            let status = self.start_hyperlink(&ppath)?;
             self.wtr.set_color(self.config.colors.path())?;
             self.wtr.write_all(ppath.as_bytes())?;
             self.wtr.reset()?;
-            hyperlink.end(&mut self.wtr)?;
+            self.interpolator.finish(status, &mut self.wtr)?;
         }
         self.wtr.write_all(&[self.config.terminator])
     }
 
     /// Starts a hyperlink span when applicable.
-    fn start_hyperlink_span(
+    fn start_hyperlink(
         &mut self,
         path: &PrinterPath,
-    ) -> io::Result<HyperlinkSpan> {
-        if self.wtr.supports_hyperlinks() {
-            if let Some(spec) = path.create_hyperlink_spec(
-                &self.config.hyperlink_pattern,
-                None,
-                None,
-                &mut self.buf,
-            ) {
-                return Ok(HyperlinkSpan::start(&mut self.wtr, &spec)?);
-            }
-        }
-        Ok(HyperlinkSpan::default())
+    ) -> io::Result<hyperlink::InterpolatorStatus> {
+        let Some(hyperpath) = path.as_hyperlink() else {
+            return Ok(hyperlink::InterpolatorStatus::inactive());
+        };
+        let values = hyperlink::Values::new(hyperpath);
+        self.interpolator.begin(&values, &mut self.wtr)
     }
 }