[IMP] add migration log file

to store all the migration logs. File reset at each migration.

.gitignore

@@ -1 +1,2 @@
 final_404_addons
+migration.log

README.md

@@ -413,10 +413,30 @@ The script works on a **copy** of the original database. You can restart as many
 
 ### Viewing Detailed Logs
 
-Odoo/OpenUpgrade logs are displayed in real-time. For a problematic migration:
+All output (scripts, Docker containers, OpenUpgrade logs) is automatically saved to `migration.log` at the project root. The file is overwritten at the start of each run (full migration or resume).
+
+```bash
+# Follow live output while also saving to file (already done automatically)
+tail -f migration.log
+
+# Search for errors after the fact
+grep -i error migration.log
+
+# View with ANSI colors preserved (less handles CRLF line endings natively)
+less -R migration.log
+
+# Plain text output without CRLF artifacts
+cat migration.log | col -b
+```
+
+> **Note:** `migration.log` is recorded via a pseudo-TTY (`script`), which preserves
+> color output in the terminal. As a side effect, the file uses `\r\n` line endings.
+> Use `less -R` or `col -b` for clean viewing.
+
+For a problematic migration:
 
 1. Note the version where the error occurs
-2. Check the logs to identify the problematic module/table
+2. Check `migration.log` to identify the problematic module/table
 3. Add a fix in the `pre_upgrade.sh` for that version
 4. Restart the migration
 

upgrade.sh

@@ -4,6 +4,13 @@ set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 source "${SCRIPT_DIR}/lib/common.sh"
 
+readonly LOG_FILE="${SCRIPT_DIR}/migration.log"
+if [[ -z "${_MIGRATION_LOGGING:-}" ]]; then
+    rm -f "$LOG_FILE"
+    export _MIGRATION_LOGGING=1
+    exec script -q -c "$(printf '%q ' "$0" "$@")" "$LOG_FILE"
+fi
+
 ####################
 # USAGE & ARGUMENTS
 ####################
@@ -225,3 +232,4 @@ log_step "POST-UPGRADE PROCESSES"
 "${SCRIPT_DIR}/scripts/finalize_db.sh" "$FINALE_DB_NAME" "$FINALE_SERVICE_NAME"
 
 log_step "UPGRADE PROCESS ENDED WITH SUCCESS"
+log_info "Full logs available at: ${LOG_FILE}"