feat: Add rev parse --reference.

It's similar to `git rev-parse --symbolic-full-name`.

Author: Byron

gitoxide-core/src/repository/revision/resolve.rs

@@ -6,6 +6,7 @@ pub struct Options {
     pub cat_file: bool,
     pub tree_mode: TreeMode,
     pub blob_format: BlobFormat,
+    pub show_reference: bool,
 }
 
 pub enum TreeMode {
@@ -46,6 +47,7 @@ pub(crate) mod function {
             cat_file,
             tree_mode,
             blob_format,
+            show_reference,
         }: Options,
     ) -> anyhow::Result<()> {
         repo.object_cache_size_if_unset(1024 * 1024);
@@ -77,6 +79,12 @@ pub(crate) mod function {
                     if cat_file {
                         return display_object(&repo, spec, tree_mode, cache.as_mut().map(|c| (blob_format, c)), out);
                     }
+                    if let Some(r) = spec.first_reference().filter(|_| show_reference) {
+                        writeln!(out, "{}", r.name)?;
+                    }
+                    if let Some(r) = spec.second_reference().filter(|_| show_reference) {
+                        writeln!(out, "{}", r.name)?;
+                    }
                     writeln!(out, "{spec}", spec = spec.detach())?;
                 }
             }

src/plumbing/main.rs

@@ -930,6 +930,7 @@ pub fn main() -> Result<()> {
                 explain,
                 cat_file,
                 tree_mode,
+                reference,
                 blob_format,
             } => prepare_and_run(
                 "revision-parse",
@@ -947,6 +948,7 @@ pub fn main() -> Result<()> {
                             format,
                             explain,
                             cat_file,
+                            show_reference: reference,
                             tree_mode: match tree_mode {
                                 revision::resolve::TreeMode::Raw => core::repository::revision::resolve::TreeMode::Raw,
                                 revision::resolve::TreeMode::Pretty => {

src/plumbing/options/mod.rs

@@ -655,6 +655,9 @@ pub mod revision {
             /// Equivalent to the `explain` subcommand.
             #[clap(short = 'e', long)]
             explain: bool,
+            /// Also show the name of the reference which led to the object.
+            #[clap(short = 'r', long, conflicts_with = "explain")]
+            reference: bool,
             /// Show the first resulting object similar to how `git cat-file` would, but don't show the resolved spec.
             #[clap(short = 'c', long, conflicts_with = "explain")]
             cat_file: bool,