Add rough but working version of rev-parse (#427)

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

@@ -8,7 +8,7 @@ use git::revision::{
 use git_repository as git;
 use std::ffi::OsString;
 
-pub fn explain(_repo: git::Repository, spec: OsString, mut out: impl std::io::Write) -> anyhow::Result<()> {
+pub fn explain(spec: OsString, mut out: impl std::io::Write) -> anyhow::Result<()> {
     let mut explain = Explain::new(&mut out);
     let spec = git::path::os_str_into_bstr(&spec)?;
     git::revision::spec::parse(spec, &mut explain)?;

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

@@ -1,2 +1,5 @@
 mod explain;
 pub use explain::explain;
+
+pub mod parse;
+pub use parse::function::parse;

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

@@ -0,0 +1,48 @@
+use crate::OutputFormat;
+
+pub struct Options {
+    pub format: OutputFormat,
+}
+
+pub(crate) mod function {
+    use super::Options;
+    use crate::OutputFormat;
+    use git_repository as git;
+    use std::ffi::OsString;
+
+    pub fn parse(
+        repo: git::Repository,
+        spec: OsString,
+        mut out: impl std::io::Write,
+        Options { format }: Options,
+    ) -> anyhow::Result<()> {
+        let spec = git::path::os_str_into_bstr(&spec)?;
+        let spec = git::RevSpec::from_bstr(spec.as_ref(), &repo)?.detach();
+
+        match format {
+            OutputFormat::Human => {
+                if let Some((kind, from, to)) = spec.range() {
+                    writeln!(&mut out, "{}", from)?;
+                    writeln!(
+                        &mut out,
+                        "{}{}",
+                        matches!(kind, git::revision::spec::Kind::Range)
+                            .then(|| "^")
+                            .unwrap_or_default(),
+                        to
+                    )?;
+                    if matches!(kind, git::revision::spec::Kind::Range) {
+                        writeln!(out, "^TBD: compute and display merge base hash")?;
+                    }
+                } else if let Some(rev) = spec.single() {
+                    writeln!(&mut out, "{}", rev)?;
+                }
+            }
+            #[cfg(feature = "serde1")]
+            OutputFormat::Json => {
+                serde_json::to_writer_pretty(&mut out, &spec)?;
+            }
+        }
+        Ok(())
+    }
+}

src/plumbing/main.rs

@@ -161,13 +161,28 @@ pub fn main() -> Result<()> {
             let repository = git::ThreadSafeRepository::discover(repository)?;
             match cmd {
                 repo::Subcommands::Revision { cmd } => match cmd {
+                    repo::revision::Subcommands::Parse { spec } => prepare_and_run(
+                        "repository-revision-parse",
+                        verbose,
+                        progress,
+                        progress_keep_open,
+                        None,
+                        move |_progress, out, _err| {
+                            core::repository::revision::parse(
+                                repository.into(),
+                                spec,
+                                out,
+                                core::repository::revision::parse::Options { format },
+                            )
+                        },
+                    ),
                     repo::revision::Subcommands::Explain { spec } => prepare_and_run(
-                        "repository-commit-describe",
+                        "repository-revision-explain",
                         verbose,
                         progress,
                         progress_keep_open,
                         None,
-                        move |_progress, out, _err| core::repository::revision::explain(repository.into(), spec, out),
+                        move |_progress, out, _err| core::repository::revision::explain(spec, out),
                     ),
                 },
                 repo::Subcommands::Commit { cmd } => match cmd {

src/plumbing/options.rs

@@ -388,6 +388,9 @@ pub mod repo {
         pub enum Subcommands {
             /// Provide the revision specification like `@~1` to explain.
             Explain { spec: std::ffi::OsString },
+            /// Try to resolve the given revspec and print the object names.
+            #[clap(visible_alias = "query")]
+            Parse { spec: std::ffi::OsString },
         }
     }