Return from user prompt without requiring Enter (#354)

* Tests: Add coverage for del / move without -f, but with prompting

Supplying the user confirmation via "yes".

* Cosmetics: Align inconsistent spacing for before (y/n) prompt

* Refactoring: Extract confirm() function

The user confirmation query had been duplicated (once) in the code.

* Refactoring: confirm(): Leave early if forced

* Return from user prompt without requiring Enter

By just reading a single character (y for yes, anything else: no).



* Tests: Ensure that only a single "y" concludes the confirmation

By switching from "yes" (that endlessly prints newline-separated "y"s) to "printf y".

* t1800-del: Add coverage for negative confirmation

Negative means "anything but y", so "n", "x", and Enter all apply.

* Cosmetics: Add trailing space after (y/n) prompt

So that the user's typed answer is not recorded directly after it, but with separation: "Foo? (y/n) y" instead of "Foo? (y/n)y".

*Compatibility: "read -N 1" is only available in Bash 4.1+

Mac OS still ships with Bash 3.2 :-( Fall back to the original prompting that requires conclusion via Enter then.
Note: Even though the tests use "printf y", this still gets accepted, as there'll be EOF after that. In real use (when stdin from the terminal stays open), a concluding Enter is mandatory, though.

Closes #152

tests/t1850-move.sh

@@ -5,6 +5,8 @@ test_description='basic move functionality
 '
 . ./test-lib.sh
 
+SPACE=' '
+
 cat > todo.txt <<EOF
 (B) smell the uppercase Roses +flowers @outside
 (A) notice the sunflowers
@@ -31,6 +33,33 @@ TODO: 1 of 1 tasks shown
 DONE: 3 of 3 tasks shown
 EOF
 
+cat > todo.txt <<EOF
+(B) smell the uppercase Roses +flowers @outside
+(A) notice the sunflowers
+EOF
+cat > done.txt <<EOF
+x 2009-02-13 make the coffee +wakeup
+x 2009-02-13 smell the coffee +wakeup
+EOF
+test_todo_session 'basic move with confirmation' <<EOF
+>>> printf y | todo.sh move 1 done.txt 2>&1 | sed -e "s#'[^']\{1,\}/\([^/']\{1,\}\)'#'\1'#g" -e 's#from .\{1,\}/\([^/]\{1,\}\) to .\{1,\}/\([^/]\{1,\}\)?#from \1 to \2?#g'
+Move '(B) smell the uppercase Roses +flowers @outside' from todo.txt to done.txt? (y/n)$SPACE
+1 (B) smell the uppercase Roses +flowers @outside
+TODO: 1 moved from 'todo.txt' to 'done.txt'.
+
+>>> todo.sh -p ls
+2 (A) notice the sunflowers
+--
+TODO: 1 of 1 tasks shown
+
+>>> todo.sh -p listfile done.txt
+3 (B) smell the uppercase Roses +flowers @outside
+1 x 2009-02-13 make the coffee +wakeup
+2 x 2009-02-13 smell the coffee +wakeup
+--
+DONE: 3 of 3 tasks shown
+EOF
+
 test_todo_session 'basic move with passed source' <<EOF
 >>> todo.sh -f move 2 todo.txt done.txt | sed "s#'[^']\{1,\}/\([^/']\{1,\}\)'#'\1'#g"
 2 x 2009-02-13 smell the coffee +wakeup