help understanding what's possible with source control integration into issue tracking software

This is related to (but not identical to) "How important is version control integration with your 开发者_Go百科bug tracking software?"

I am currently using JIRA as issue/task tracking software with a small team, for potential evaluation for broader use in our company. Because we use SurroundSCM, and JIRA does not support either SurroundSCM or the general SCCI, I can't use the two together and I have a hard time understanding the tangible benefits of integration with issue tracking + source control integration.

If you are experienced in this area, could you please post (one feature per answer please) a tangible example of how issue tracking + source control integration has made your job easier / more reliable? I can only think of one area which I will post too.

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Easily referencing issues in source-control commits, and source-control revisions in issues.

If the source control software and issue tracking systems have a web interface, then it's possible to use URLs as linkage, but this is kind of cumbersome.