Fix deadlock in getCommit

[scottrw93]

Description

We are seeing infrequent deadlocks using the GHRepository::getCommit from a threadpool.

thread dump snippet

 #17072 daemon prio=5 os_prio=0 cpu=943046.99ms elapsed=8709.52s tid=0x00007f3ca82a5fb0 nid=0x8de9 runnable [0x00007f3903353000] java.lang.Thread.State: RUNNABLE at java.util.WeakHashMap.get(java.base@11.0.5/WeakHashMap.java:404) at org.kohsuke.github.GHRepository.getCommit(GHRepository.java:1627) at

WeakHashMap is not threadsafe, and using Collections.synchronisedMap is the recommended way of making it so if this client should be usable concurrently?

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[codecov]

Codecov Report

Merging #1460 (f29f24a) into main (aa363a5) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main    #1460   +/-   ##
=========================================
  Coverage     78.76%   78.76%           
  Complexity     2100     2100           
=========================================
  Files           201      201           
  Lines          6390     6390           
  Branches        359      359           
=========================================
  Hits           5033     5033           
  Misses         1149     1149           
  Partials        208      208           

Impacted Files	Coverage Δ
src/main/java/org/kohsuke/github/GHRepository.java	68.34% <100.00%> (ø)

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[bitwiseman]

I'm not clear why we're even using WeakHashMap here, but in terms of making theses particular fields not deadlock, this seems like a low risk change.

[scottrw93]

I think WeakHashMap is used just to reduce memory footprint in #468. Similar idea explained here