Crash while using SSH transport #1700
Description
While investigating fetching remotes in Objective-Git, I got a crash (stack trace at the end of the issue).
It seems the stack trace is wrong, because using the debugger I can step inside _git_ssh_setup_conn until t->owner->cred_acquire_cb, and here the crash happens. I imagine that's because I didn't provide a callback through git_remote_set_cred_acquire_cb but I'm not sure...
libgit2: v0.16.0-3099-gc8a39f9
* thread #1: tid = 0x1d07, 0x0000000000000000, stop reason = step over
frame #0: 0x0000000000000000
frame #1: 0x000000010021c07f ObjectiveGit`ssh_uploadpack_ls(t=0x00000001129538b0, url=0x000000011293ee50, stream=0x00007fff5fbfdde0) + 47 at ssh.c:405
frame #2: 0x000000010021bedb ObjectiveGit`_ssh_action(stream=0x00007fff5fbfdde0, subtransport=0x00000001129538b0, url=0x000000011293ee50, action=GIT_SERVICE_UPLOADPACK_LS) + 91 at ssh.c:464
frame #3: 0x0000000100217453 ObjectiveGit`git_smart__connect(transport=0x0000000102172200, url=0x00000001130423b0, cred_acquire_cb=0x0000000000000000, cred_acquire_payload=0x0000000000000000, direction=0, flags=0) + 323 at smart.c:96
frame #4: 0x00000001001eeac1 ObjectiveGit`git_remote_connect(remote=0x00000001130423f0, direction=GIT_DIRECTION_FETCH) + 353 at remote.c:549
frame #5: 0x0000000100243bf7 ObjectiveGit`-[GTRemote fetchWithError:](self=0x0000000113036aa0, _cmd=0x000000010007b3c2, error=0x00007fff5fbfe008) + 343 at GTRemote.m:118
frame #6: 0x00000001000414d3 GitX`-[PBGitRepository beginFetchFromRemoteForRef:](self=0x0000000109d04d40, _cmd=0x0000000100077d51, ref=0x0000000112e83ae0) + 1411 at PBGitRepository.m:652
frame #7: 0x0000000100022104 GitX`-[PBRefController fetchRemote:](self=0x000000011112ba60, _cmd=0x0000000100079953, sender=0x000000011302a6a0) + 212 at PBRefController.m:40
frame #8: 0x00007fff8fe98959 AppKit`-[NSApplication sendAction:to:from:] + 342
frame #9: 0x00007fff8ffce36c AppKit`-[NSMenuItem _corePerformAction] + 406
frame #10: 0x00007fff8ffce05a AppKit`-[NSCarbonMenuImpl performActionWithHighlightingForItemAtIndex:] + 133
frame #11: 0x00007fff8fcbb20f AppKit`-[NSMenu _internalPerformActionForItemAtIndex:] + 36
frame #12: 0x00007fff8fcbb097 AppKit`-[NSCarbonMenuImpl _carbonCommandProcessEvent:handlerCallRef:] + 135
frame #13: 0x00007fff8ffc7165 AppKit`NSSLMMenuEventHandler + 342
frame #14: 0x00007fff8d97dd1a HIToolbox`DispatchEventToHandlers(EventTargetRec*, OpaqueEventRef*, HandlerCallRec*) + 1206
frame #15: 0x00007fff8d97d1e9 HIToolbox`SendEventToEventTargetInternal(OpaqueEventRef*, OpaqueEventTargetRef*, HandlerCallRec*) + 410
frame #16: 0x00007fff8d992fc9 HIToolbox`SendEventToEventTarget + 40
frame #17: 0x00007fff8d9c9ca9 HIToolbox`SendHICommandEvent(unsigned int, HICommand const*, unsigned int, unsigned int, unsigned char, void const*, OpaqueEventTargetRef*, OpaqueEventTargetRef*, OpaqueEventRef**) + 443
frame #18: 0x00007fff8d96ea21 HIToolbox`SendMenuCommandWithContextAndModifiers + 59
frame #19: 0x00007fff8d96e9d3 HIToolbox`SendMenuItemSelectedEvent + 254
frame #20: 0x00007fff8d96e85f HIToolbox`FinishMenuSelection(SelectionData*, MenuResult*, MenuResult*) + 94
frame #21: 0x00007fff8dae4e79 HIToolbox`PopUpMenuSelectCore(MenuData*, Point, double, Point, unsigned short, unsigned int, Rect const*, unsigned short, unsigned int, Rect const*, Rect const*, __CFString const*, OpaqueMenuRef**, unsigned short*) + 1673
frame #22: 0x00007fff8dae4794 HIToolbox`_HandlePopUpMenuSelection7 + 629
frame #23: 0x00007fff9004a56b AppKit`_NSSLMPopUpCarbonMenu3 + 3916
frame #24: 0x00007fff900495f8 AppKit`-[NSCarbonMenuImpl _popUpContextMenu:withEvent:forView:withFont:] + 189
frame #25: 0x00007fff901a3ff3 AppKit`-[NSMenu _popUpContextMenu:withEvent:forView:withFont:] + 200
frame #26: 0x00007fff90369937 AppKit`-[NSView rightMouseDown:] + 130
frame #27: 0x00007fff90098cfb AppKit`-[NSControl _rightMouseUpOrDown:] + 534
frame #28: 0x00007fff8fe8db81 AppKit`-[NSWindow sendEvent:] + 8504
frame #29: 0x00007fff8fe89644 AppKit`-[NSApplication sendEvent:] + 5761
frame #30: 0x00007fff8fd9f21a AppKit`-[NSApplication run] + 636
frame #31: 0x00007fff8fd43bd6 AppKit`NSApplicationMain + 869
frame #32: 0x0000000100054d5b GitX`main(argc=3, argv=0x00007fff5fbff848) + 43 at main.m:15
frame #33: 0x0000000100001984 GitX`start + 52