Next element of the loop

Question

I’m trying to implement a commit search algorithm between two tags with the command git log tag1...tag2. For this I used the command git tag that returns me the tags of a repository.

With this result, I thought of iterating on it by executing the command git

for tag in $Tags
do
    git log $tag .. $proximaTag
done

My question is: How to get the value of the next tag? In this case, how to get the value of the next item in the array?

Have some better way to implement this kind of algorithm?

Answer 1

In the case of the loop for you will not be able to catch the next element from the list but it is possible to use the loop while and the command shift to do so:

show_commits(){    
    first_tag=${1}
    while true; do
        shift
        next_tag=${1}
        if [[ $next_tag == '' ]]; then
            break
        else
            git log "${first_tag}".."${next_tag}" --pretty=%H
            echo
            first_tag=$next_tag
        fi
    done
}

show_commits $( git tag | tac )

The list of tags is generated directly by Git and the command tac serves to reverse her order) and all of it is sent to the function as the arguments $1, $2, $3 etc. But you can do something direct like "show_commits v1.2.3 v1.2.2 v1.0.0".

However, despite receiving all of them, the function will use only one argument, see that only one argument -- ${1} -- is used to assign the value to variables first_tag and next_tag.

Therein comes the shift that takes care of shifting the arguments to the left, so $1 turns $0, $2 turns $1 etc and $0 is always discarded in the process... this is done until the variable next_tag receives an empty value, which means there are no more values and the loop is broken.