Conditional Build Jobs in Travis CI: A Decision Guide

The Problem: Running Builds Only When Needed

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You want to save CI minutes and reduce queue times by running builds only for specific branches or tags not on every push. Travis CI supports branch-based conditions but implementing them correctly requires understanding the syntax and limitations.

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Supported Options Compared

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Approach	Syntax	Scope	Limitations
Branch pattern matching	branches: with only: or except:	Repository-level	Simple glob matching; no full regex; case-sensitive
Tag-based builds	tags: with only: or except:	Repository-level	Requires protected tags on VCS provider; plan-dependent
Stage conditions	stage: with if: expressions	Job-level	Available only on Pro and Enterprise plans
Script-level conditionals	Standard shell conditionals in script:	Job-level	Build still provisions; only script execution is conditional

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Trade-offs

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Branch patterns are the most widely available option and prevent unnecessary jobs from starting. However, Travis CI uses simple glob matching not full regular expressions so patterns like release/* work but release/v\\d+ does not.

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Tag-based builds are useful for release pipelines but require setting up protected tags in your VCS provider. This adds operational overhead but ensures only intentional releases trigger builds.

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Stage conditions offer fine-grained control but are gated behind paid plans. If you need complex workflows factor this cost into your decision.

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Script-level conditionals are the most flexible but waste build minutes because Travis still provisions the job environment. Use this only when other options are insufficient.

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Implementation Example: Branch-Based Conditional Build

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language: python\npython:\n  - 3.9\n  - 3.10\n  - 3.11\nbranches:\n  only:\n    - main\n    - /^release/.*/\ncache: pip\ninstall:\n  - pip install -r requirements.txt\n\nscript:\n  - pytest tests/\n\nafter_success:\n  - pip install coveralls\n  - coveralls

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Verification Steps

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1. Push a test commit to a non-matching branch (e.g., feature/test). Check the Travis CI UI: no build should be created.
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2. Push to the main branch. A build should start with the matrix of Python versions.
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3. Create a branch named release/v1.0 and push. Verify the build runs.
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4. Check job logs for Cache hit messages to confirm caching is working.
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Important Limitations

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• Travis CI's free tier has usage limits; conditional builds help but do not eliminate them.
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• Pattern matching is case-sensitive; Release/* will not match release/*.
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• The branches: key applies to all jobs in the build; individual jobs cannot override it.
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• Protected tags must be configured in your VCS provider before Travis CI will build them.
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