feat: gix rev previous-branches subcommand (#427)

README.md

@@ -44,6 +44,7 @@ Please see _'Development Status'_ for a listing of all crates and their capabili
     * **revision**
         * [x] **explain** - show what would be done while parsing a revision specification like `HEAD~1`
         * [x] **parse** - Show which objects a revspec resolves to
+        * [x] **previous-branches** - list all previously checked out branches, powered by the ref-log.
     * **free** - no git repository necessary
         * **pack**
           * [x] [verify](https://asciinema.org/a/352942)

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

@@ -3,3 +3,29 @@ pub use explain::explain;
 
 pub mod parse;
 pub use parse::function::parse;
+
+mod previous_branches {
+    use crate::OutputFormat;
+    use anyhow::Context;
+    use git_repository as git;
+
+    pub fn function(repo: git::Repository, mut out: impl std::io::Write, format: OutputFormat) -> anyhow::Result<()> {
+        let branches = repo
+            .head()?
+            .prior_checked_out_branches()?
+            .context("The reflog for HEAD is required")?;
+        match format {
+            OutputFormat::Human => {
+                for (name, id) in branches {
+                    writeln!(out, "{} {}", id, name)?;
+                }
+            }
+            #[cfg(feature = "serde1")]
+            OutputFormat::Json => {
+                serde_json::to_writer_pretty(&mut out, &branches)?;
+            }
+        }
+        Ok(())
+    }
+}
+pub use previous_branches::function as previous_branches;

src/plumbing/main.rs

@@ -516,8 +516,16 @@ pub fn main() -> Result<()> {
             },
         ),
         Subcommands::Revision(cmd) => match cmd {
+            revision::Subcommands::PreviousBranches => prepare_and_run(
+                "revision-previousbranches",
+                verbose,
+                progress,
+                progress_keep_open,
+                None,
+                move |_progress, out, _err| core::repository::revision::previous_branches(repository()?, out, format),
+            ),
             revision::Subcommands::Explain { spec } => prepare_and_run(
-                "commit-describe",
+                "revision-explain",
                 verbose,
                 progress,
                 progress_keep_open,

src/plumbing/options.rs

@@ -190,6 +190,8 @@ pub mod revision {
             #[clap(min_values = 1)]
             specs: Vec<std::ffi::OsString>,
         },
+        /// Return the names and hashes of all previously checked-out branches.
+        PreviousBranches,
     }
 }