Today I had a bit of a struggle with the Jenkins EnvInject Plugin while trying to inject custom variables from a properties file into my MSBuild step. Everything that I added to the Properties Content field was successfully injected, and looking at the log, the EnvInject reported successfully injecting my file envVars.properties variables as well.
I used PowerShell to retrieve the current Git branch and echoed it into the envVars.properties file shown in the image above, which also turned out to be the culprit.
# $currentBranch set elsewhere. echo CURRENT_GIT_BRANCH=$currentBranch > envVars.properties
All this gave me was an error about EnvInject having problems with the Byte Order Mark (BOM). Using a without-BOM encoding causes EnvInject to report success, but nothing gets injected.
# $currentBranch set elsewhere. echo CURRENT_GIT_BRANCH=$currentBranch | Set-Content -Encoding ASCII -Path ".\envVars.properties"
So, generating the envVars.properties file in PowerShell using ASCII encoding, as above, sorts the issue.