Select last commit or full branch history for analysis of #bumps

[sbe-arg]

Variable BRANCH_HISTORY" full|last allows to select the length of the history for finding bump keywords.

As per examples:

history='full'
declare -A history_type=( 
    ["last"]="$(git show -s --format=%B)" \
    ["full"]="$(git log master..HEAD --format=%B)" \
)
log=${history_type[${history}]}
printf "History:\n---\n%s\n---\n" "$log"
History:
---
history type


POC log
---

history='last'
declare -A history_type=( 
    ["last"]="$(git show -s --format=%B)" \
    ["full"]="$(git log master..HEAD --format=%B)" \
)
log=${history_type[${history}]}
printf "History:\n---\n%s\n---\n" "$log"
History:
---
history type
---

fixes #211

[sammcj]

Just that one tiny comment / question otherwise ok to approve!

[sammcj]

lgtm!

[sbe-arg]

Been sick and afk will merge in the next few days.