Here, for once, the French makes it simpler 
There is no “tch” pronunciation in French unless there is a “t” before the “ch”, that has then to be pronounced.
Chocolat is pronounced sho-co-la like in shingle or sharp.
Tchad (the African country) is pronounced t-sha-d like in… chocolate or cheese.
There are extremely few words in French that start with “tch” or contain this “tch” combination. So you might as well forget it and just make an educated guess if you ever meet one.
Back to the French “ch”… il will always be pronounced “sh”
PS : For the scholars… no pun intended, we do have words where “ch” is pronounced “k”. And no one is going to make a fuss about them as most French don’t prononce them well, anyway