For example, suppose we have a single letter 'A' in a file. The line in the file has
length 1. We are not including newlines at the end of the line.

The SHA 256 hash of 'A' is 559AEAD08264D5795D3909718CDD05ABD49572E84FE55590EEF31A88A08FDFFD
To force the number of leaves in the initial Merkle tree to be even, we create a new leaf
with 'A'. So far, our initial list looks like  'A' --> 'A' ---||

We construct the first list of hashes from the initial list of values.

Initial list of hashes is h('A') --->  h('A') ---||

The actual hashes appear as follows:
559AEAD08264D5795D3909718CDD05ABD49572E84FE55590EEF31A88A08FDFFD
559AEAD08264D5795D3909718CDD05ABD49572E84FE55590EEF31A88A08FDFFD

We concatenate these two hashes and hash the concatenation to compute a new hash.

BE263C0044B95044951327B0D9ABBD7E4E3719CC1AE59B57DF059945616219C1

Since we have only a single line in the file, we are done. 

The Merkel root is BE263C0044B95044951327B0D9ABBD7E4E3719CC1AE59B57DF059945616219C1