How to search for a term currently in code AND added within the last 6 months?

I want to search source control for files with a specific term and with these conditions:

1. It has to be in the latest version of the code in the branch I'm searching. So an instance that was added 3 months ago but was removed 1 month ago should NOT count.

2. It has to have been added within the last 6 months. So an instance currently in the code that was added in 2020 should NOT count.

Is there a reasonably straightforward way to do a search like this using either the command line or any visual tools?

git log --all --since=6.months.ago -p --word-diff=porcelain -S term \
| awk '/^diff/ { file=substr($NF,3) } /^+/ && /term/ { print file }' | sort -u

will get you the list of files that have had that term added in the last six months. List the files that still have it with git grep -l and the common entries are your payload. You can add --pickaxe-regex and the log will treat term as a regex so you can beef up the selectivity if the bare substring match gets too much cruft.

if you want string still here, git grep will help
then you blame the result of the git grep
you filter on the date

ggb.sh:

ggb() {
    limit=$(date +%s -d '-6 months' )
    echo $limit
    git grep -n $1 | while IFS=: read i j k; do
    git blame -L $j,$j $i -p|awk -v limit="$limit" -v file="$i"  'NR==1 {commit=$1} NR==8 {date=$2} END { if (date > limit) print file " " commit}'
done
}
 ggb $1

usage:

ggb.sh "foo"

Will output filename and commit adding the string

Details:

git grep output is read with while IFS=: read i j k; do loop.

Then git blame is used with -p to get porcelain output

git blame porcelain format is described here

with awk we get the first word of the first line NR==1 {commit=$1}

then second work of line 8 NR==8 {date=$2} to get the committer-time

The time limit is computed with date +%s -d '-6 months'
then the path and the limit is used into awk command with -v:

awk -v limit="$limit" -v file="$i"