feat(sync): add conflict prediction before sync (#141)

Author: auswm85

Cargo.toml

@@ -3,17 +3,17 @@ resolver = "3"
 members = ["crates/*"]
 
 [workspace.package]
-version = "0.7.0"
+version = "0.8.0"
 edition = "2024"
 license = "MIT"
 repository = "https://github.com/auswm85/rung"
 rust-version = "1.88"
 
 [workspace.dependencies]
 # Internal crates
-rung-core = { version = "0.7.0", path = "crates/rung-core" }
-rung-git = { version = "0.7.0", path = "crates/rung-git" }
-rung-github = { version = "0.7.0", path = "crates/rung-github" }
+rung-core = { version = "0.8.0", path = "crates/rung-core" }
+rung-git = { version = "0.8.0", path = "crates/rung-git" }
+rung-github = { version = "0.8.0", path = "crates/rung-github" }
 
 # Git operations
 git2 = "0.19"

README.md

@@ -168,11 +168,22 @@ Sync the stack by rebasing all branches when the base moves forward.
 
 ```bash
 rung sync                # Sync all branches
+rung sync --check        # Predict conflicts before syncing
 rung sync --dry-run      # Preview what would happen
 rung sync --base develop # Sync against a different base branch
 ```
 
-If conflicts occur:
+Check for conflicts before syncing:
+
+```bash
+$ rung sync --check
+⚠️  Potential conflicts detected:
+
+  feature-a → main
+    • file.rs (abc123: "Add feature")
+```
+
+If conflicts occur during sync:
 
 ```bash
 # Resolve conflicts, then:
@@ -185,6 +196,7 @@ rung sync --abort
 
 **Options:**
 
+- `--check` - Predict conflicts without performing sync *(v0.8.0+)*
 - `--dry-run` - Show what would be done without making changes
 - `--continue` - Continue after resolving conflicts
 - `--abort` - Abort and restore from backup

crates/rung-cli/src/commands/mod.rs

@@ -121,6 +121,11 @@ pub enum Commands {
         #[arg(long)]
         dry_run: bool,
 
+        /// Predict conflicts without performing sync.
+        /// Shows which branches would have conflicts and which files.
+        #[arg(long)]
+        check: bool,
+
         /// Continue a paused sync after resolving conflicts.
         #[arg(long, name = "continue")]
         continue_: bool,