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