Bash: an assignment in a loop body that reads the loop variable is not listed on later commands #249

Problem

An assignment inside a loop body that reads the loop variable does not appear in the assignment facts of the later commands in that body.

Example:

for i in 1 2; do GIT_DIR=/tmp/r$i; git status; done

• If GIT_DIR is in the launch environment, git status runs with GIT_DIR=/tmp/r1 and then with GIT_DIR=/tmp/r2.
• SST does not list the GIT_DIR assignment on the git status occurrence.

Impact

A consumer that reads the assignment facts (for example, an approval digest) does not see that the environment of git status can change.

Expected

• List the assignment on each later command in the body, with the value set when SST proves it (/tmp/r1, /tmp/r2), or Unknown.
• Keep MayAffectProcessEnvironment true unless the complete-environment rule (Prove that an unexported Bash assignment stays out of a child #248) proves otherwise.

Found by the review of #248 (dev has the same gap).