feat: gix merge-base for the CLI

For now it only supports the standard merge-base, but more derivatives
can be added easily on demand.

gitoxide-core/src/repository/merge_base.rs

@@ -0,0 +1,31 @@
+use crate::OutputFormat;
+use anyhow::bail;
+
+pub fn merge_base(
+    mut repo: gix::Repository,
+    first: String,
+    others: Vec<String>,
+    mut out: impl std::io::Write,
+    format: OutputFormat,
+) -> anyhow::Result<()> {
+    if format != OutputFormat::Human {
+        bail!("Only 'human' format is currently supported");
+    }
+    repo.object_cache_size_if_unset(50 * 1024 * 1024);
+    let first_id = repo.rev_parse_single(first.as_str())?;
+    let other_ids: Vec<_> = others
+        .iter()
+        .cloned()
+        .map(|other| repo.rev_parse_single(other.as_str()).map(gix::Id::detach))
+        .collect::<Result<_, _>>()?;
+
+    let cache = repo.commit_graph_if_enabled()?;
+    let bases = repo.merge_bases_many_with_cache(first_id, &other_ids, cache.as_ref())?;
+    if bases.is_empty() {
+        bail!("No base found for {first} and {others}", others = others.join(", "))
+    }
+    for id in bases {
+        writeln!(&mut out, "{id}")?;
+    }
+    Ok(())
+}

gitoxide-core/src/repository/mod.rs

@@ -44,6 +44,8 @@ mod fsck;
 pub use fsck::function as fsck;
 pub mod index;
 pub mod mailmap;
+mod merge_base;
+pub use merge_base::merge_base;
 pub mod odb;
 pub mod remote;
 pub mod revision;

gix/src/repository/revision.rs

@@ -52,11 +52,10 @@ impl crate::Repository {
         let two = two.into();
         let cache = self.commit_graph_if_enabled()?;
         let mut graph = self.revision_graph(cache.as_ref());
-        let bases =
-            gix_revision::merge_base(one, &vec![two], &mut graph)?.ok_or(super::merge_base::Error::NotFound {
-                first: one,
-                second: two,
-            })?;
+        let bases = gix_revision::merge_base(one, &[two], &mut graph)?.ok_or(super::merge_base::Error::NotFound {
+            first: one,
+            second: two,
+        })?;
         Ok(bases[0].attach(self))
     }
 
@@ -76,7 +75,7 @@ impl crate::Repository {
         let one = one.into();
         let two = two.into();
         let mut graph = self.revision_graph(cache);
-        let bases = gix_revision::merge_base(one, &vec![two], &mut graph)?.ok_or(
+        let bases = gix_revision::merge_base(one, &[two], &mut graph)?.ok_or(
             super::merge_base_with_cache::Error::NotFound {
                 first: one,
                 second: two,

src/plumbing/main.rs

@@ -141,6 +141,17 @@ pub fn main() -> Result<()> {
     }
 
     match cmd {
+        Subcommands::MergeBase(crate::plumbing::options::merge_base::Command { first, others }) => prepare_and_run(
+            "merge-base",
+            trace,
+            verbose,
+            progress,
+            progress_keep_open,
+            None,
+            move |_progress, out, _err| {
+                core::repository::merge_base(repository(Mode::Lenient)?, first, others, out, format)
+            },
+        ),
         Subcommands::Worktree(crate::plumbing::options::worktree::Platform { cmd }) => match cmd {
             crate::plumbing::options::worktree::SubCommands::List => prepare_and_run(
                 "worktree-list",

src/plumbing/options/mod.rs

@@ -138,6 +138,7 @@ pub enum Subcommands {
     Config(config::Platform),
     #[cfg(feature = "gitoxide-core-tools-corpus")]
     Corpus(corpus::Platform),
+    MergeBase(merge_base::Command),
     Worktree(worktree::Platform),
     /// Subcommands that need no git repository to run.
     #[clap(subcommand)]
@@ -268,6 +269,17 @@ pub mod status {
     }
 }
 
+pub mod merge_base {
+    #[derive(Debug, clap::Parser)]
+    #[command(about = "A command for calculating all merge-bases")]
+    pub struct Command {
+        /// A revspec for the first commit.
+        pub first: String,
+        /// Revspecs for the other commits to compute the merge-base with.
+        pub others: Vec<String>,
+    }
+}
+
 pub mod worktree {
     #[derive(Debug, clap::Parser)]
     #[command(about = "Commands for handling worktrees")]