In /usr/bin/what-patch line 58:
	files=`lsdiff -z ../$(dpkg-parsechangelog -SSource)_$(dpkg-parsechangelog -SVersion).diff.gz 2>/dev/null | grep -v 'debian/'`
              ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.
                            ^-----------------------------^ SC2046: Quote this to prevent word splitting.
                                                            ^-- SC2046: Quote this to prevent word splitting.

Did you mean: 
	files=$(lsdiff -z ../$(dpkg-parsechangelog -SSource)_$(dpkg-parsechangelog -SVersion).diff.gz 2>/dev/null | grep -v 'debian/')


In /usr/bin/what-patch line 69:
if fgrep -q quilt debian/source/format 2>/dev/null; then
   ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.


In /usr/bin/what-patch line 78:
for filename in $(echo "debian/rules"; grep ^include debian/rules | fgrep -v '$(' | awk '{print $2}')
                                                                    ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.
                                                                             ^--^ SC2016: Expressions don't expand in single quotes, use double quotes for that.


In /usr/bin/what-patch line 80:
	fgrep patchsys.mk "$filename" | grep -q -v "^#" && {
        ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.


In /usr/bin/what-patch line 87:
	fgrep quilt "$filename" | grep -q -v "^#" && { echo "quilt"; exit 0; }
        ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.


In /usr/bin/what-patch line 88:
	fgrep dbs-build.mk "$filename" | grep -q -v "^#" && {
        ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.


In /usr/bin/what-patch line 95:
	fgrep dpatch "$filename" | grep -q -v "^#" && {
        ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.


In /usr/bin/what-patch line 102:
	fgrep '*.diff' "$filename" | grep -q -v "^#" && {
        ^---^ SC2197: fgrep is non-standard and deprecated. Use grep -F instead.

For more information:
  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
  https://www.shellcheck.net/wiki/SC2016 -- Expressions don't expand in singl...
  https://www.shellcheck.net/wiki/SC2197 -- fgrep is non-standard and depreca...