[tbb-bugs] #15456 [Tor Browser]: Prevent incremental updates from failing for Linux hackers

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#15456: Prevent incremental updates from failing for Linux hackers
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 Reporter:  mikeperry             |          Owner:  tbb-team
     Type:  defect                |         Status:  new
 Priority:  normal                |      Milestone:
Component:  Tor Browser           |        Version:
 Keywords:  TorBrowserTeam201504  |  Actual Points:
Parent ID:                        |         Points:
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 While working on Bug #13375, I realized that people who hack up their TBB
 startup scripts are going to download the full MAR update if the
 incremental tries to change one of the startup scripts that they have
 modified. This may end up being a waste of bandwidth, depending on how
 commonly we push updates to these scripts, and how common it is that users
 modify them.

 Originally, I was going to try to sneak this in to 4.5a5, but I am now
 convinced that it is too risky for an uncertain amount of improvement.

 We should instead keep an eye on how often Linux users tend to download
 the full TBB MAR as opposed to the incremental, and if we notice a spike
 for instances where we have updated these files, then we should perform
 this optimization.

 We can start by counting the fraction of Linux users download the full MAR
 for 4.5a5 (where the start-tor-browser script did change) and compare that
 to the fraction of Linux users who downloaded the full MAR for 4.5a1-4
 (where the start-tor-browser script did not change). If there is a huge
 difference, we can consider trying to deploy this change.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15456>
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