feat: add support for base branch

script/upstream/README.md

@@ -20,6 +20,9 @@ bun run merge.ts --version v1.1.49
 
 # Dry-run to preview what would happen
 bun run merge.ts --version v1.1.49 --dry-run
+
+# Use a different base branch (e.g., for incremental merges)
+bun run merge.ts --version v1.1.50 --base-branch catrielmuller/kilo-opencode-v1.1.44
 ```
 
 ## Scripts
@@ -207,22 +210,66 @@ The only remaining conflicts are files with **actual code differences** - files
 
 ```
 Options:
-  --version <version>  Target upstream version (e.g., v1.1.49)
-  --commit <hash>      Target upstream commit hash
-  --dry-run            Preview changes without applying them
-  --no-push            Don't push branches to remote
-  --report-only        Only generate conflict report
-  --verbose            Enable verbose logging
-  --author <name>      Author name for branch prefix
+  --version <version>    Target upstream version (e.g., v1.1.49)
+  --commit <hash>        Target upstream commit hash
+  --base-branch <name>   Base branch to merge into (default: dev)
+  --dry-run              Preview changes without applying them
+  --no-push              Don't push branches to remote
+  --report-only          Only generate conflict report
+  --verbose              Enable verbose logging
+  --author <name>        Author name for branch prefix
 ```
 
 ### analyze.ts
 
 ```
 Options:
-  --version <version>  Target upstream version
-  --commit <hash>      Target commit hash
-  --output <file>      Output file for report
+  --version <version>    Target upstream version
+  --commit <hash>        Target commit hash
+  --base-branch <name>   Base branch to analyze from (default: dev)
+  --output <file>        Output file for report
+```
+
+## Using Custom Base Branches
+
+By default, upstream merges start from the `dev` branch. However, you can use `--base-branch` to start from a different branch. This is useful for:
+
+### Incremental Merges
+
+When working on multiple upstream versions, you can create a chain of merge PRs:
+
+```bash
+# First merge: v1.1.44 into dev
+bun run merge.ts --version v1.1.44
+
+# Create PR: catrielmuller/kilo-opencode-v1.1.44 -> dev
+
+# Second merge: v1.1.50 based on the previous PR (without waiting for approval)
+bun run merge.ts --version v1.1.50 --base-branch catrielmuller/kilo-opencode-v1.1.44
+
+# Create PR: catrielmuller/kilo-opencode-v1.1.50 -> catrielmuller/kilo-opencode-v1.1.44
+# OR: catrielmuller/kilo-opencode-v1.1.50 -> dev (once first PR is merged)
+```
+
+### Benefits
+
+- **Work in parallel**: Don't wait for PR approval to start the next merge
+- **Isolation**: Each merge is independent and easier to review
+- **Flexibility**: Can adjust the PR chain as needed
+- **Cleaner history**: Related merges can be grouped together
+
+### Example Workflow
+
+```bash
+# 1. Analyze next version from your WIP branch
+bun run analyze.ts --version v1.1.50 --base-branch catrielmuller/kilo-opencode-v1.1.44
+
+# 2. Run the merge
+bun run merge.ts --version v1.1.50 --base-branch catrielmuller/kilo-opencode-v1.1.44
+
+# 3. Create PR from catrielmuller/kilo-opencode-v1.1.50
+#    - Target: catrielmuller/kilo-opencode-v1.1.44 (if first PR not merged yet)
+#    - Target: dev (if first PR is already merged)
 ```
 
 ## Manual Conflict Resolution

script/upstream/analyze.ts

@@ -7,19 +7,21 @@
  * Usage:
  *   bun run script/upstream/analyze.ts --version v1.1.49
  *   bun run script/upstream/analyze.ts --commit abc123
+ *   bun run script/upstream/analyze.ts --version v1.1.49 --base-branch catrielmuller/kilo-opencode-v1.1.44
  */
 
 import { $ } from "bun"
 import * as git from "./utils/git"
 import * as version from "./utils/version"
 import * as report from "./utils/report"
-import { defaultConfig } from "./utils/config"
+import { defaultConfig, loadConfig } from "./utils/config"
 import { header, info, success, warn, error, divider, list } from "./utils/logger"
 
 interface AnalyzeOptions {
   version?: string
   commit?: string
   output?: string
+  baseBranch?: string
 }
 
 function parseArgs(): AnalyzeOptions {
@@ -41,11 +43,17 @@ function parseArgs(): AnalyzeOptions {
     options.output = args[outputIdx + 1]
   }
 
+  const baseBranchIdx = args.indexOf("--base-branch")
+  if (baseBranchIdx !== -1 && args[baseBranchIdx + 1]) {
+    options.baseBranch = args[baseBranchIdx + 1]
+  }
+
   return options
 }
 
 async function main() {
   const options = parseArgs()
+  const config = loadConfig(options.baseBranch ? { baseBranch: options.baseBranch } : undefined)
 
   header("Upstream Change Analysis")
 
@@ -93,7 +101,7 @@ async function main() {
   info("Analyzing changes...")
 
   // Use commit hash directly since we may not have the tag fetched locally
-  const conflicts = await report.analyzeConflicts(target.commit, defaultConfig.baseBranch, defaultConfig.keepOurs)
+  const conflicts = await report.analyzeConflicts(target.commit, config.baseBranch, config.keepOurs)
 
   // Group by type
   const byType = new Map<string, report.ConflictFile[]>()
@@ -149,7 +157,7 @@ async function main() {
     timestamp: new Date().toISOString(),
     upstreamVersion: target.version,
     upstreamCommit: target.commit,
-    baseBranch: defaultConfig.baseBranch,
+    baseBranch: config.baseBranch,
     mergeBranch: "",
     totalConflicts: conflicts.length,
     conflicts,

script/upstream/merge.ts

@@ -10,6 +10,7 @@
  * Options:
  *   --version <version>  Target upstream version (e.g., v1.1.49)
  *   --commit <hash>      Target upstream commit hash
+ *   --base-branch <name> Base branch to merge into (default: dev)
  *   --dry-run            Preview changes without applying them
  *   --no-push            Don't push branches to remote
  *   --report-only        Only generate conflict report, don't merge
@@ -52,6 +53,7 @@ import { resolveLockFileConflicts, regenerateLockFiles } from "./transforms/lock
 interface MergeOptions {
   version?: string
   commit?: string
+  baseBranch?: string
   dryRun: boolean
   push: boolean
   reportOnly: boolean
@@ -84,6 +86,11 @@ function parseArgs(): MergeOptions {
     options.author = args[authorIdx + 1]
   }
 
+  const baseBranchIdx = args.indexOf("--base-branch")
+  if (baseBranchIdx !== -1 && args[baseBranchIdx + 1]) {
+    options.baseBranch = args[baseBranchIdx + 1]
+  }
+
   return options
 }
 
@@ -109,7 +116,7 @@ async function createBackupBranch(baseBranch: string): Promise<string> {
 
 async function main() {
   const options = parseArgs()
-  const config = loadConfig()
+  const config = loadConfig(options.baseBranch ? { baseBranch: options.baseBranch } : undefined)
 
   if (options.verbose) {
     logger.setVerbose(true)