What tools do you use to make software updates&patches

[goo...@agensoft.com]

Hello.
What tools/approaches do you currently use to provide your customers
with the latest version of your software product or any other
freshness-critical files?

If you currently use any self-made tool or approach then do you think
of changing it to some standard solution?

What features do you think an ideal patch maker must provide (including

both patch building and applying aspects)?

What can be the main reason for using a patch building utility to
provide your customers with compact patch modules (containing only
differences between files) instead of full-version software packages?

Thanks in advance.
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Pavel Shamsutdinov
www.agensoft.com