[PATCH 3/4] tools/mount-flatpak: Move more code to mount_commit()

[Demi Marie Obenour <demiobenour@gmail.com>]

Make mount_commit() responsible for not only mounting the commit tree,
but also for opening the source subdirectory and creating the
destination subdirectory.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
---
 tools/mount-flatpak/src/main.rs | 82 ++++++++++++++++++++---------------------
 1 file changed, 39 insertions(+), 43 deletions(-)

diff --git a/tools/mount-flatpak/src/main.rs b/tools/mount-flatpak/src/main.rs
index 68a1f6ea308387a9471682c927d3a71439ab69e4..b40402b1b15729bdd2228025850efe8d87a48e3b 100644
--- a/tools/mount-flatpak/src/main.rs
+++ b/tools/mount-flatpak/src/main.rs
@@ -43,7 +43,7 @@ mod metadata;
 
 use std::borrow::Cow;
 use std::env::{ArgsOs, args_os};
-use std::ffi::OsStr;
+use std::ffi::{OsStr, OsString};
 use std::io;
 use std::os::unix::prelude::*;
 use std::path::{Path, PathBuf};
@@ -67,12 +67,21 @@ fn open_subdir(root: &Root, path: &Path) -> Result<Root, Error> {
 }
 
 fn mount_commit(
-    source_commit: &dyn AsFd,
+    source_installation: &Root,
+    source_path: &Path,
     target_installation: &Root,
-    path: &Path,
-) -> Result<(), String> {
+    target_path: &Path,
+    kind: &str,
+) -> Result<(Root, OsString), String> {
+    let source_commit_parent_dir = open_subdir(source_installation, source_path)
+        .map_err(|e| format!("opening source {kind} commit parent: {e}"))?;
+    let commit = source_commit_parent_dir
+        .readlink("active")
+        .map_err(|e| format!("reading active {kind} commit: {e}"))?;
+    let source_root = open_subdir(&source_commit_parent_dir, &commit)
+        .map_err(|e| format!("opening source {kind} commit: {e}"))?;
     let source_commit_tree = open_tree(
-        source_commit,
+        &source_root,
         "",
         OpenTreeFlags::AT_EMPTY_PATH
             | OpenTreeFlags::OPEN_TREE_CLONE
@@ -81,7 +90,7 @@ fn mount_commit(
     )
     .map_err(|e| format!("cloning source commit tree: {e}"))?;
     let target_commit_dir = target_installation
-        .mkdir_all(path, &PermissionsExt::from_mode(0o700))
+        .mkdir_all(target_path, &PermissionsExt::from_mode(0o700))
         .map_err(|e| format!("creating target commit directory: {e}"))?;
     move_mount(
         source_commit_tree,
@@ -90,7 +99,8 @@ fn mount_commit(
         "",
         MoveMountFlags::MOVE_MOUNT_F_EMPTY_PATH | MoveMountFlags::MOVE_MOUNT_T_EMPTY_PATH,
     )
-    .map_err(|e| format!("mounting commit: {e}"))
+    .map_err(|e| format!("mounting commit: {e}"))?;
+    Ok((source_root, commit.as_os_str().to_owned()))
 }
 
 fn run(mut args: ArgsOs) -> Result<(), String> {
@@ -129,11 +139,13 @@ fn run(mut args: ArgsOs) -> Result<(), String> {
     let target_installation_dir =
         Root::from_fd(target_installation_dir).with_resolver_flags(ResolverFlags::NO_SYMLINKS);
 
-    let mut full_app_path = installation_path.join("app");
-    full_app_path.push(&app);
-    full_app_path.push("current");
-    let arch_and_branch = source_installation_dir
-        .readlink(&full_app_path)
+    let mut app_path = PathBuf::new();
+    app_path.push("app");
+    app_path.push(&app);
+    let source_app_dir = open_subdir(&source_installation_dir, &app_path)
+        .map_err(|e| format!("opening source flatpak app: {e}"))?;
+    let arch_and_branch = source_app_dir
+        .readlink("current")
         .map_err(|e| format!("reading current app arch and branch: {e}"))?;
     let mut components = arch_and_branch.components();
     let arch = components.next().unwrap().as_os_str();
@@ -142,21 +154,16 @@ fn run(mut args: ArgsOs) -> Result<(), String> {
         return Err("can't infer branch from \"current\" link".to_string());
     }
 
-    full_app_path.pop();
-    full_app_path.push(&arch_and_branch);
-    full_app_path.push("active");
-    let commit = source_installation_dir
-        .readlink(&full_app_path)
-        .map_err(|e| format!("reading active app commit: {e}"))?
-        .into_os_string();
-
-    full_app_path.pop();
-    full_app_path.push(&commit);
-    let source_app_dir = open_subdir(&source_installation_dir, &full_app_path)
-        .map_err(|e| format!("opening source app directory: {e}"))?;
+    let (source_commit_dir, commit) = mount_commit(
+        &source_app_dir,
+        &app_path.join(&arch_and_branch),
+        &target_installation_dir,
+        &arch_and_branch,
+        "app",
+    )?;
 
-    let metadata = source_installation_dir
-        .resolve(&full_app_path.join("metadata"))
+    let metadata = source_commit_dir
+        .resolve("metadata")
         .map_err(|e| format!("resolving app metadata: {e}"))?;
 
     let metadata_stat =
@@ -172,25 +179,14 @@ fn run(mut args: ArgsOs) -> Result<(), String> {
 
     let runtime =
         extract_runtime(metadata).map_err(|e| format!("reading runtime from metadata: {e}"))?;
+    let runtime_path = Path::new("runtime").join(runtime);
 
-    let mut full_runtime_path = installation_path.join("runtime");
-    full_runtime_path.push(runtime);
-    full_runtime_path.push("active");
-    let runtime_commit = source_installation_dir
-        .readlink(&full_runtime_path)
-        .map_err(|e| format!("reading active runtime commit: {e}"))?
-        .into_os_string();
-
-    full_runtime_path.pop();
-    full_runtime_path.push(&runtime_commit);
-    let source_runtime_dir = open_subdir(&source_installation_dir, &full_runtime_path)
-        .map_err(|e| format!("opening source runtime directory: {e}"))?;
-
-    mount_commit(&source_app_dir, &target_installation_dir, &full_app_path)?;
-    mount_commit(
-        &source_runtime_dir,
+    let (_, runtime_commit) = mount_commit(
+        &source_installation_dir,
+        &runtime_path,
         &target_installation_dir,
-        &full_runtime_path,
+        &runtime_path,
+        "runtime",
     )?;
 
     target_installation_dir

-- 
2.52.0