feat: add new gix cat command.

gitoxide-core/src/repository/cat.rs

@@ -0,0 +1,62 @@
+use crate::repository::revision::resolve::{BlobFormat, TreeMode};
+use anyhow::{anyhow, Context};
+use gix::diff::blob::ResourceKind;
+use gix::filter::plumbing::driver::apply::Delay;
+use gix::revision::Spec;
+
+pub fn display_object(
+    repo: &gix::Repository,
+    spec: Spec<'_>,
+    tree_mode: TreeMode,
+    cache: Option<(BlobFormat, &mut gix::diff::blob::Platform)>,
+    mut out: impl std::io::Write,
+) -> anyhow::Result<()> {
+    let id = spec.single().context("rev-spec must resolve to a single object")?;
+    let header = id.header()?;
+    match header.kind() {
+        gix::object::Kind::Tree if matches!(tree_mode, TreeMode::Pretty) => {
+            for entry in id.object()?.into_tree().iter() {
+                writeln!(out, "{}", entry?)?;
+            }
+        }
+        gix::object::Kind::Blob if cache.is_some() && spec.path_and_mode().is_some() => {
+            let (path, mode) = spec.path_and_mode().expect("is present");
+            match cache.expect("is some") {
+                (BlobFormat::Git, _) => unreachable!("no need for a cache when querying object db"),
+                (BlobFormat::Worktree, cache) => {
+                    let platform = cache.attr_stack.at_entry(path, Some(mode.into()), &repo.objects)?;
+                    let object = id.object()?;
+                    let mut converted = cache.filter.worktree_filter.convert_to_worktree(
+                        &object.data,
+                        path,
+                        &mut |_path, attrs| {
+                            let _ = platform.matching_attributes(attrs);
+                        },
+                        Delay::Forbid,
+                    )?;
+                    std::io::copy(&mut converted, &mut out)?;
+                }
+                (BlobFormat::Diff | BlobFormat::DiffOrGit, cache) => {
+                    cache.set_resource(id.detach(), mode.kind(), path, ResourceKind::OldOrSource, &repo.objects)?;
+                    let resource = cache.resource(ResourceKind::OldOrSource).expect("just set");
+                    let data = resource
+                        .data
+                        .as_slice()
+                        .ok_or_else(|| anyhow!("Binary data at {} cannot be diffed", path))?;
+                    out.write_all(data)?;
+                }
+            }
+        }
+        _ => out.write_all(&id.object()?.data)?,
+    }
+    Ok(())
+}
+
+pub(super) mod function {
+    use crate::repository::revision::resolve::TreeMode;
+
+    pub fn cat(repo: gix::Repository, revspec: &str, out: impl std::io::Write) -> anyhow::Result<()> {
+        super::display_object(&repo, repo.rev_parse(revspec)?, TreeMode::Pretty, None, out)?;
+        Ok(())
+    }
+}

gitoxide-core/src/repository/mod.rs

@@ -19,6 +19,8 @@ pub enum PathsOrPatterns {
 
 #[cfg(feature = "archive")]
 pub mod archive;
+pub mod cat;
+pub use cat::function::cat;
 pub mod commit;
 pub mod config;
 mod credential;

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

@@ -25,17 +25,12 @@ pub enum BlobFormat {
 pub(crate) mod function {
     use std::ffi::OsString;
 
-    use anyhow::{anyhow, Context};
-    use gix::diff::blob::ResourceKind;
-    use gix::filter::plumbing::driver::apply::Delay;
     use gix::revision::Spec;
 
     use super::Options;
+    use crate::repository::cat::display_object;
     use crate::repository::revision::resolve::BlobFormat;
-    use crate::{
-        repository::{revision, revision::resolve::TreeMode},
-        OutputFormat,
-    };
+    use crate::{repository::revision, OutputFormat};
 
     pub fn resolve(
         mut repo: gix::Repository,
@@ -109,52 +104,4 @@ pub(crate) mod function {
         }
         Ok(())
     }
-
-    fn display_object(
-        repo: &gix::Repository,
-        spec: Spec<'_>,
-        tree_mode: TreeMode,
-        cache: Option<(BlobFormat, &mut gix::diff::blob::Platform)>,
-        mut out: impl std::io::Write,
-    ) -> anyhow::Result<()> {
-        let id = spec.single().context("rev-spec must resolve to a single object")?;
-        let header = id.header()?;
-        match header.kind() {
-            gix::object::Kind::Tree if matches!(tree_mode, TreeMode::Pretty) => {
-                for entry in id.object()?.into_tree().iter() {
-                    writeln!(out, "{}", entry?)?;
-                }
-            }
-            gix::object::Kind::Blob if cache.is_some() && spec.path_and_mode().is_some() => {
-                let (path, mode) = spec.path_and_mode().expect("is present");
-                match cache.expect("is some") {
-                    (BlobFormat::Git, _) => unreachable!("no need for a cache when querying object db"),
-                    (BlobFormat::Worktree, cache) => {
-                        let platform = cache.attr_stack.at_entry(path, Some(mode.into()), &repo.objects)?;
-                        let object = id.object()?;
-                        let mut converted = cache.filter.worktree_filter.convert_to_worktree(
-                            &object.data,
-                            path,
-                            &mut |_path, attrs| {
-                                let _ = platform.matching_attributes(attrs);
-                            },
-                            Delay::Forbid,
-                        )?;
-                        std::io::copy(&mut converted, &mut out)?;
-                    }
-                    (BlobFormat::Diff | BlobFormat::DiffOrGit, cache) => {
-                        cache.set_resource(id.detach(), mode.kind(), path, ResourceKind::OldOrSource, &repo.objects)?;
-                        let resource = cache.resource(ResourceKind::OldOrSource).expect("just set");
-                        let data = resource
-                            .data
-                            .as_slice()
-                            .ok_or_else(|| anyhow!("Binary data at {} cannot be diffed", path))?;
-                        out.write_all(data)?;
-                    }
-                }
-            }
-            _ => out.write_all(&id.object()?.data)?,
-        }
-        Ok(())
-    }
 }

src/plumbing/main.rs

@@ -1117,6 +1117,15 @@ pub fn main() -> Result<()> {
                 },
             ),
         },
+        Subcommands::Cat { revspec } => prepare_and_run(
+            "cat",
+            trace,
+            verbose,
+            progress,
+            progress_keep_open,
+            None,
+            move |_progress, out, _err| core::repository::cat(repository(Mode::Lenient)?, &revspec, out),
+        ),
         Subcommands::Commit(cmd) => match cmd {
             commit::Subcommands::Verify { rev_spec } => prepare_and_run(
                 "commit-verify",

src/plumbing/options/mod.rs

@@ -130,6 +130,11 @@ pub enum Subcommands {
     /// Interact with submodules.
     #[clap(alias = "submodules")]
     Submodule(submodule::Platform),
+    /// Show whatever object is at the given spec.
+    Cat {
+        /// The object to print to stdout.
+        revspec: String,
+    },
     IsClean,
     IsChanged,
     /// Show which git configuration values are used or planned.