What do the symbols *1 or &2 mean in Travis CI deployment scripts? -

i'm following guide using travis deploy aws codedeploy. in docs point .travis.yml example contains following code:

deploy:   - provider: s3     access_key_id: akiaj4xzhimnkp3wgghq     secret_access_key: &1       secure: <key>     local_dir: dpl_cd_upload     skip_cleanup: true     on: &2       repo: travis-ci/cat-party     bucket: catparty-codedeploy   - provider: codedeploy     access_key_id: akiaj4xzhimnkp3wgghq     secret_access_key: *1     bucket: catparty-codedeploy     key: latest.zip     bundle_type: zip     application: catpartydemoapplication     deployment_group: productiondemofleet     on: *2 

i've got working , understand flow (first uploads zip file s3, deploys file codedeploy). i'm struggling syntax: on: &2 line in s3 section, , on: *2 part in codedeploy section. these lines doing?

i ask because want modify configuration deploy different codedeploy group depending on whether commit has given tag, eg:

on:   tags: true   all_branches: true   condition: "$travis_tag =~ ^release.*$" 

... because i'm not clear on: *2 doing (and can't find in docs), i'm uncertain how proceed. tips?

those symbols , features bring part of yaml itself. they're supported reduce duplication efforts in yaml file.

for instance, section prefixed & stores subsequent structure reference name 2. 2 references repo: travis-ci/cat-party.

on: &2 repo: travis-ci/cat-party

the reference name can alphanumeric set of characters make things more expressive.

on other hand, * used resolve reference want reuse it.

so in following section yaml parser resolve *2 structure stored: repo: travis-ci/cat-party:

on: *2

this feature saves duplication, can handy in several aspects of .travis.yml file.