The issue is a different one, I believe you're considering one specific situation while there are others to ponder. What would happen if someone copy & pasted part of the hash, or had some tool that always reduced that output to the first few digits, or other situations like these, how would you be able to tell that the user was actually after the oldest commit?
It seems much easier to indicate there's a problem, a conflict, and let the user solve it.
The issue is a different one, I believe you're considering one specific situation while there are others to ponder. What would happen if someone copy & pasted part of the hash, or had some tool that always reduced that output to the first few digits, or other situations like these, how would you be able to tell that the user was actually after the oldest commit? It seems much easier to indicate there's a problem, a conflict, and let the user solve it.