The following snippets help obtain information about the number of lines of code that were changed in a git repository.

Get commit information between two dates

git log --oneline --stat --after="2019-05-28" --before="2019-08-28" --pretty="@%h" | grep -v \| |  tr "\n" " "  |  tr "@" "\n"

Get the lines of code that were changed between two commits or two tags

git diff --shortstat <taga> <tagb>

Get the number of lines of code (ESLOC) for a repository for a given file type

git ls-files | grep -P ".*\.filetype$" | xargs wc -l  

where filetype is the type of file whose lines you want to count.