Implement support for fetching raw Git object bytes

Summary: Extend the existing admin command to allow fetching the raw bytes of a Git object. This is useful for debugging.

Reviewed By: andreacampi

Differential Revision: D68717363

fbshipit-source-id: 36a39b4d18ff1299dbfb1d0dc7dae85da909f98e

eden/mononoke/tools/admin/src/commands/git_objects/fetch.rs

@@ -5,13 +5,19 @@
  * GNU General Public License version 2.
  */
 
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
 use anyhow::Context;
 use anyhow::Result;
 use clap::Args;
 use context::CoreContext;
 use git_types::fetch_git_object;
+use git_types::fetch_git_object_bytes;
 use git_types::fetch_non_blob_git_object;
 use git_types::GitIdentifier;
+use git_types::HeaderState;
 use gix_object::Object::Blob;
 use gix_object::Object::Commit;
 use gix_object::Object::Tag;
@@ -26,6 +32,9 @@ pub struct FetchArgs {
     /// The Git SHA1 object id (in hex form) of the object that is to be fetched
     #[clap(long)]
     id: GitSha1,
+    /// Store the raw bytes of the git object in the specified file instead of printing the parsed object
+    #[clap(long)]
+    raw_bytes_file: Option<PathBuf>,
     /// The type of the git object to be fetched. Required if the object can be git blob
     #[clap(long, requires = "size")]
     ty: Option<String>,
@@ -34,7 +43,16 @@ pub struct FetchArgs {
     size: Option<u64>,
 }
 
-pub async fn fetch(repo: &Repo, ctx: &CoreContext, mut fetch_args: FetchArgs) -> Result<()> {
+pub async fn fetch(repo: &Repo, ctx: &CoreContext, fetch_args: FetchArgs) -> Result<()> {
+    if fetch_args.raw_bytes_file.is_some() {
+        fetch_bytes(repo, ctx, fetch_args).await?;
+    } else {
+        fetch_object(repo, ctx, fetch_args).await?;
+    }
+    Ok(())
+}
+
+async fn fetch_object(repo: &Repo, ctx: &CoreContext, mut fetch_args: FetchArgs) -> Result<()> {
     let ty = fetch_args.ty.take();
     let size = fetch_args.size.take();
     let git_object = match (ty, size) {
@@ -62,3 +80,20 @@ pub async fn fetch(repo: &Repo, ctx: &CoreContext, mut fetch_args: FetchArgs) ->
     };
     Ok(())
 }
+
+async fn fetch_bytes(repo: &Repo, ctx: &CoreContext, fetch_args: FetchArgs) -> Result<()> {
+    let git_object_bytes = fetch_git_object_bytes(
+        ctx,
+        repo.repo_blobstore.clone(),
+        &GitIdentifier::Basic(fetch_args.id),
+        HeaderState::Included,
+    )
+    .await?;
+    let mut file = File::create(
+        fetch_args
+            .raw_bytes_file
+            .ok_or_else(|| anyhow::anyhow!("Path is required for writing raw output bytes"))?,
+    )?;
+    file.write_all(&git_object_bytes)?;
+    Ok(())
+}