I tried to setup a test project, using a git project connecting through ssh.
After selecting the ssh credential and adding the git URL (ssh://git@bitbucket.org/CLIENT/test.git) I get the following message:
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Failed to connect to repository : Command "C:/Progra~1/Git/bin/git.exe -c core.askpass=true ls-remote -h ssh://git@bitbucket.org/CLIENT/test.git HEAD" returned status code 128:
stdout:
stderr: 'C:\Program' is not recognized as an internal or external command,
operable program or batch file.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
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My setup:
Jenkins: 1.633
GIT client plugin: 1.19.0
GIT plugin: 2.4.0

Jenkins Git Configuration is set to: C:/Progra~1/Git/bin/git.exe
Git 2.6.1 from https://git-scm.com/downloads.