From b83f6bdf7f8d8f5cef2a57fa3932b6a0e0988db1 Mon Sep 17 00:00:00 2001
From: Sebastian Thiel <sebastian.thiel@icloud.com>
Date: Wed, 3 Aug 2022 16:46:10 +0800
Subject: [PATCH] feat: `--cat-file` flag for `gix rev parse` to cat instead of
 resolving. (#427)

---
 .../src/repository/revision/resolve.rs        | 30 ++++++++++++++++---
 src/plumbing/main.rs                          | 12 ++++++--
 src/plumbing/options.rs                       |  6 +++-
 3 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/gitoxide-core/src/repository/revision/resolve.rs b/gitoxide-core/src/repository/revision/resolve.rs
index ef4e89ebabe..d58851715c9 100644
--- a/gitoxide-core/src/repository/revision/resolve.rs
+++ b/gitoxide-core/src/repository/revision/resolve.rs
@@ -3,10 +3,11 @@ use crate::OutputFormat;
 pub struct Options {
     pub format: OutputFormat,
     pub explain: bool,
+    pub cat_file: bool,
 }
 
 pub(crate) mod function {
-    use anyhow::bail;
+    use anyhow::{bail, Context};
     use std::ffi::OsString;
 
     use git_repository as git;
@@ -19,7 +20,11 @@ pub(crate) mod function {
         mut repo: git::Repository,
         specs: Vec<OsString>,
         mut out: impl std::io::Write,
-        Options { format, explain }: Options,
+        Options {
+            format,
+            explain,
+            cat_file,
+        }: Options,
     ) -> anyhow::Result<()> {
         repo.object_cache_size_if_unset(1024 * 1024);
 
@@ -30,8 +35,11 @@ pub(crate) mod function {
                         return revision::explain(spec, out);
                     }
                     let spec = git::path::os_str_into_bstr(&spec)?;
-                    let spec = repo.rev_parse(spec)?.detach();
-                    writeln!(out, "{spec}")?;
+                    let spec = repo.rev_parse(spec)?;
+                    if cat_file {
+                        return display_object(spec, out);
+                    }
+                    writeln!(out, "{spec}", spec = spec.detach())?;
                 }
             }
             #[cfg(feature = "serde1")]
@@ -55,4 +63,18 @@ pub(crate) mod function {
         }
         Ok(())
     }
+
+    fn display_object(spec: git::revision::Spec<'_>, mut out: impl std::io::Write) -> anyhow::Result<()> {
+        let id = spec.single().context("rev-spec must resolve to a single object")?;
+        let object = id.object()?;
+        match object.kind {
+            git::object::Kind::Tree => {
+                for entry in object.into_tree().iter() {
+                    writeln!(out, "{}", entry?)?;
+                }
+            }
+            _ => out.write_all(&object.data)?,
+        }
+        Ok(())
+    }
 }
diff --git a/src/plumbing/main.rs b/src/plumbing/main.rs
index 029f9a071e7..7385b9d8f6f 100644
--- a/src/plumbing/main.rs
+++ b/src/plumbing/main.rs
@@ -532,7 +532,11 @@ pub fn main() -> Result<()> {
                 None,
                 move |_progress, out, _err| core::repository::revision::explain(spec, out),
             ),
-            revision::Subcommands::Resolve { specs, explain } => prepare_and_run(
+            revision::Subcommands::Resolve {
+                specs,
+                explain,
+                cat_file,
+            } => prepare_and_run(
                 "revision-parse",
                 verbose,
                 progress,
@@ -543,7 +547,11 @@ pub fn main() -> Result<()> {
                         repository()?,
                         specs,
                         out,
-                        core::repository::revision::resolve::Options { format, explain },
+                        core::repository::revision::resolve::Options {
+                            format,
+                            explain,
+                            cat_file,
+                        },
                     )
                 },
             ),
diff --git a/src/plumbing/options.rs b/src/plumbing/options.rs
index ecdcb0fb736..05647f71751 100644
--- a/src/plumbing/options.rs
+++ b/src/plumbing/options.rs
@@ -187,10 +187,14 @@ pub mod revision {
         /// Try to resolve the given revspec and print the object names.
         #[clap(visible_alias = "query", visible_alias = "parse")]
         Resolve {
-            /// If set, instead of resolving a rev-spec, explain what would be done for the first spec.
+            /// Instead of resolving a rev-spec, explain what would be done for the first spec.
+            ///
             /// Equivalent to the `explain` subcommand.
             #[clap(short = 'e', long)]
             explain: 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,
             /// rev-specs like `@`, `@~1` or `HEAD^2`.
             #[clap(required = true)]
             specs: Vec<std::ffi::OsString>,