How does eval stop the pathspec errors in this script? - bash

Question

I want to automate the many version control steps of Git. I was successful until I used git commit -S -m ${var} in my Bash script. This line gives me (pathspec errors x # of word) - 1... unless I use eval. How does eval make my script work?
I thought this article had the answer, but my issue involves a string, not an array.
Gif video of the broken vs. working Bash script
Broken code
brokenCommitCode () {
# Give it a multi-word, space-separated message
read -p 'Commit message (use quotes): ' commitMsg
commitMsg="'${commitMsg}'"
echo ${commitMsg}
git add -A &&
git commit -S -m ${commitMsg}
}
Working code
workingCommitCode () {
read -p 'Commit message (use quotes): ' commitMsg
commitMsg="'${commitMsg}'"
echo ${commitMsg}
git add -A &&
eval git commit -S -m ${commitMsg}
}
I expected the brokenCommitCode to commit properly with the message I enter on the prompt. The actual result is a pathspec error when it reaches git commit -S -m ${commitMsg}. How does eval make this work?
I'm using GNU bash, version 4.4.19(1)-release (x86_64-pc-msys) with git version 2.16.2.windows.1 on a Windows 8.1 PC.

Answer 1

Correct fix is
funname() {
read -p 'Commit message (use quotes): ' commitMsg
echo "${commitMsg}"
git add -A &&
git commit -S -m "${commitMsg}"
}
Why eval seems to fix:
single quotes where added to commitMsg variable (seems intent was to prevent message argument to be split on a whitespace)
looking what happens with the following message:
commitMsg="this is a message"
git commit -S -m ${commitMsg}
git commit -S -m this is a message
[error because "is" "a" "message" are taken as different additional arguments]
however it doesn't prevent because single quote is not re-interpreted but is like any other character in variable content
following with the example
git commit -S -m ${commitMsg}
git commit -S -m \'this is a message\'
[error "is" "a" "message'" are taken as different additional arguments]
with eval the single quotes are re-interpreted but also any other character which has a particular meaning in bash (;, &, ${..}, ..)
Suppose for example the following commit message which can inject arbitrary command.
commitMsg="message'; ls -l; echo 'done"
git commit -S -m 'message'; ls -l; echo 'done'