Update airflow config update to show breaking config changes by default

[sunank200]

airflow.cfg in Airflow 2. x usually has 2000+ lines of configs. Users typically want to change only the configurations causing issues in airflow migrations rather than dealing with a long list of config changes they may not fully understand.

This PR refines the airflow config update to better serve users upgrading to Airflow 3.0. Key changes include:

• Dry-Run by default (Breaking Changes Only):
  The airflow config update command now defaults to a dry run (same as --dry-run) and displays only the breaking configuration changes. This avoids overwhelming users with recommended but non-critical changes. The breaking changes here are the configs causing errors/ warnings / deprecations.

• New CLI Arguments:

  • --fix: Applies the breaking changes instead of a dry run.
  • --all-recommendations: When used with either --dry-run or --fix, it includes all recommended changes (i.e., non-breaking ones) in addition to breaking ones.

CLI Command Argument:

• Dry-run mode (showing only breaking changes):

  airflow config update
  

I tested it default airflow.cfg from Airflow 2.10.5:

• Dry-run mode including all recommendations (breaking + non-breaking):

  airflow config update --all-recommendations
  

I tested it default airflow.cfg from Airflow 2.10.5:

• Apply only the breaking changes:

  airflow config update --fix
  

I tested it default airflow.cfg from Airflow 2.10.5:

• Apply all recommended changes (both breaking and non-breaking):

  airflow config update --fix --all-recommendations
  

• Update only specific sections (e.g. core and database):

  airflow config update --section core,database
  

• Update only specific options (e.g. sql_alchemy_conn and dag_concurrency):

  airflow config update --option sql_alchemy_conn,dag_concurrency
  

• Ignore a specific section (e.g. webserver):

  airflow config update --ignore-section webserver
  

• Ignore specific options (e.g. smtp_user and session_lifetime_days):

  airflow config update --ignore-option smtp_user,session_lifetime_days
  

Breaking config changes

---

Section	Option	Change Type	Old Value / Condition	New Value / New Config Name
core	executor	Default Value Change	SequentialExecutor	LocalExecutor
logging	log_filename_template	Removal	{{ ti.dag_id }}/{{ ti.task_id }}/{{ ts }}/{{ try_number }}.log	The actual replacement value will be updated after defaults are loaded from config.yml
logging	log_filename_template	Removal	dag_id={{ ti.dag_id }}/run_id={{ ti.run_id }}/task_id={{ ti.task_id }}/{% if ti.map_index >= 0 %}map_index={{ ti.map_index }}/{% endif %}attempt={{ try_number }}.log	The actual replacement value will be updated after defaults are loaded from config.yml
webserver	web_server_host	Rename	web_server_host	host (in [api])
webserver	web_server_port	Rename	web_server_port	port (in [api])
webserver	workers	Rename	workers	workers (in [api])
webserver	web_server_ssl_cert	Rename	web_server_ssl_cert	ssl_cert (in [api])
webserver	web_server_ssl_key	Rename	web_server_ssl_key	ssl_key (in [api])
webserver	access_logfile	Rename	access_logfile	access_logfile (in [api])
scheduler	catchup_by_default	Default Value Change	True	False
scheduler	dag_dir_list_interval	Rename	dag_dir_list_interval	refresh_interval (in [dag_processor])
triggerer	default_capacity	Rename	default_capacity	capacity (in [triggerer])
elasticsearch	log_id_template	Removal	{dag_id}-{task_id}-{logical_date}-{try_number}	Removed

closes: #49202

---

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Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in airflow-core/newsfragments.

[Copilot]

Pull Request Overview

This PR updates the Airflow configuration update command to show only breaking configuration changes by default in dry-run mode and introduces new CLI arguments to optionally apply and include all recommendations.

• Change default behavior of airflow config update to display only breaking changes in dry-run mode.
• Introduce new CLI arguments (--fix and --all-recommendations) to control application of configuration changes.
• Update tests and documentation strings to reflect the revised behavior.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
airflow-core/tests/unit/cli/commands/test_config_command.py	Updates tests to check for dry-run messages and configuration backup, but uses an incorrect CLI flag.
airflow-core/src/airflow/cli/commands/config_command.py	Refactors configuration change message formatting and enhances the update_config command to include new flags.
airflow-core/src/airflow/cli/cli_config.py	Adds definitions for new CLI parameters (--fix and --all-recommendations) for the config update command.

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

airflow-core/src/airflow/cli/commands/config_command.py:837

• The flag '--all-recommendation' is inconsistent with the '--all-recommendations' defined in cli_config.py. Consider standardizing the flag name to avoid confusion.

        --all-recommendation: flag (optional)

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

airflow-core/src/airflow/cli/commands/config_command.py:983

• [nitpick] Consider revising the message 'Dry-run is mode enabled.' to 'Dry-run mode enabled.' to improve clarity.

console.print("[blue]Dry-run is mode enabled. To apply above airflow.cfg run the command with `--fix`.[/blue]")

[Lee-W]

I think we also cover some of the rules in newsfragments in this PR. Could you please also update the corresponding newsfragments?

You can list the rule todos through uv run scripts/ci/pre_commit/significant_newsfragments_checker.py

Thanks!