feat(git): add worktree branch roots

Author: pcristin

Makefile.cbm

@@ -218,6 +218,9 @@ TRACES_SRCS = src/traces/traces.c
 # Watcher module (new)
 WATCHER_SRCS = src/watcher/watcher.c
 
+# Git context module (new)
+GIT_SRCS = src/git/git_context.c
+
 # CLI module (new)
 CLI_SRCS = src/cli/cli.c src/cli/progress_sink.c src/cli/hook_augment.c
 
@@ -283,7 +286,7 @@ TRE_CFLAGS = -std=c11 -g -O1 -w -Ivendored/tre
 YYJSON_SRC = vendored/yyjson/yyjson.c
 
 # All production sources
-PROD_SRCS = $(FOUNDATION_SRCS) $(STORE_SRCS) $(CYPHER_SRCS) $(MCP_SRCS) $(DISCOVER_SRCS) $(GRAPH_BUFFER_SRCS) $(PIPELINE_SRCS) $(SIMHASH_SRCS) $(SEMANTIC_SRCS) $(TRACES_SRCS) $(WATCHER_SRCS) $(CLI_SRCS) $(UI_SRCS) $(YYJSON_SRC)
+PROD_SRCS = $(FOUNDATION_SRCS) $(STORE_SRCS) $(CYPHER_SRCS) $(MCP_SRCS) $(DISCOVER_SRCS) $(GRAPH_BUFFER_SRCS) $(PIPELINE_SRCS) $(SIMHASH_SRCS) $(SEMANTIC_SRCS) $(TRACES_SRCS) $(WATCHER_SRCS) $(GIT_SRCS) $(CLI_SRCS) $(UI_SRCS) $(YYJSON_SRC)
 EXISTING_C_SRCS = $(EXTRACTION_SRCS) $(LSP_SRCS) $(TS_RUNTIME_SRC) \
                   $(GRAMMAR_SRCS) $(AC_LZ4_SRCS) $(ZSTD_SRCS) $(SQLITE_WRITER_SRC)
 

scripts/security-allowlist.txt

@@ -22,6 +22,10 @@ src/watcher/watcher.c:cbm_popen:git working tree status (git_is_dirty)
 src/watcher/watcher.c:cbm_popen:git file count (git_file_count)
 src/watcher/watcher.c:popen:via cbm_popen wrapper calls
 
+# ── Git context: git metadata resolution (repo paths validated via cbm_validate_shell_arg) ──
+src/git/git_context.c:cbm_popen:git rev-parse/symbolic-ref/merge-base metadata lookup
+src/git/git_context.c:popen:via cbm_popen wrapper call
+
 # ── MCP server: search and change detection ────────────────────────────────
 src/mcp/mcp.c:cbm_popen:search_code via grep (pattern in temp file, path validated)
 src/mcp/mcp.c:cbm_popen:detect_changes via git diff (args validated)