Add prefixes to identifiers with `--file-scope`. (#8282)

This change only affects the case where `--file-scope` is used
and more than one file is specified on the command line.

In this case, identifiers will be prefixed with a string
derived from the file path, to disambiguate them. For example,
an identifier `foo` in `contents/file1.txt` will become
`contents__file1.txt__foo`.  Links will be adjusted accordingly:
if `file2.txt` links to `file1.txt#foo`, then the link will
be changed to point to `#file1.txt__foo`.  Similarly, a link
to `file1.txt` will point to `#file1.txt`.  A Div with an
identifier derived from the file path will be added around
each file's content, so that links to files will still work.

Closes #6384.

[API change]: Text.Pandoc.Shared exports `textToIdentifier`.

1 files changed, 5 insertions, 0 deletions

diff --git a/test/command/file2.txt b/test/command/file2.txt
new file mode 100644
index 000000000..20ee06c8c
--- /dev/null
+++ b/test/command/file2.txt
@@ -0,0 +1,5 @@
+## Zed
+
+[foo]: baz
+
+[foo]