I've searched around the Atlassian site [1][2], but I can't find any stated end-of-life policy for SourceTree. Specifically, how long will SourceTree 2.x be maintained with patches and bug fixes?
[1] Atlassian Support End of Life Policy
[2] Atlassian Support Offerings
2018-08-28 Edit:
More specifically, I work for a US Federal agency which has an approved software list. In order to get SourceTree (or any software) on this list, I need to prove vendor support for the software (free or paid). "Support" here, is less about customer/technical support (which is provided for free via the Atlassian Community here), but rather more about patches/bug fixes/software maintenance support.
I need to provide an answer to the following (emphasis mine):
"I need documentation proving vendor support for this software. This documentation could be a signed vendor software support contract or purchase order with the period of performance, a specific URL citation demonstrating current full support to end-of-life, or an email/URL from the vendor stating support is provided at no additional charge, or fully approved ITPRs can be submitted as proof of support. Support must include patches and bug-fixes."