update entry for $(ROLL.NAME[n]) variable

[kazuoteramoto]

Thank you for taking the time to help the darktable documentation!

Please include a link to the Pull Request that you are documenting

darktable-org/darktable#19531

Tell us a little bit about this pull request

Copying the help text from the gtk entry to the docs.

[elstoc]

I think this needs some more detail, to describe what "levels" are in this context

[kazuoteramoto]

Thanks for the review!

One suggestion is

diff --git i/content/special-topics/variables.md w/content/special-topics/variables.md
index 32d3053..8f559b6 100644
--- i/content/special-topics/variables.md
+++ w/content/special-topics/variables.md
@@ -18,7 +18,7 @@ darktable supports variable substitution in a number of modules and preference s
 The following variables are available, though they may not all be applicable in every context:

 ```diff
-$(ROLL.NAME[n])            roll of the input image, n: levels used, default n=1
+$(ROLL.NAME[n])            roll of the input image, where n is the folder levels, starting from the right, default n=1
 $(FILE.FOLDER)             folder containing the input image
 $(FILE.NAME)               basename of the input image
 $(FILE.EXTENSION)          extension of the input image

I can also link to content/module-reference/utility-modules/shared/collections.md

Any opinion of what is best?

[elstoc]

You can't do a link since this is a fenced code block. Will think about wording, but yeah something like that will probably work.

You might need to extend the description down to the next line to ensure it doesn't wrap on small screens

[kazuoteramoto]

Another slight variation, split in two lines. I used the term "film roll" because it appears in other parts of the documentation.

diff --git i/content/special-topics/variables.md w/content/special-topics/variables.md
index 32d3053..88d8cc4 100644
--- i/content/special-topics/variables.md
+++ w/content/special-topics/variables.md
@@ -18,7 +18,8 @@ darktable supports variable substitution in a number of modules and preference s
 The following variables are available, though they may not all be applicable in every context:

 ```
-$(ROLL.NAME[n])            roll of the input image, n: levels used, default n=1
+$(ROLL.NAME[n])            film roll of the input image, where n specifies the folder level
+                           counting from the right, default n=1
 $(FILE.FOLDER)             folder containing the input image
 $(FILE.NAME)               basename of the input image
 $(FILE.EXTENSION)          extension of the input image

[elstoc]

Looks good