doc: add script to compute texi files dependencies

Replace the inline awk script with a Perl script which tracks the
dependencies recursively.

This allows to correctly track dependencies for files including files
with a second level include (for example: ffmpeg-devices.texi ->
devices.texi -> outdevs.texi).

This also adds a dependency on perl for computing the dependencies, which
should not be a problem since perl is already required all the way for
building documentation.

configure

@@ -2214,8 +2214,8 @@ ffserver_extralibs='$ldl'
 # documentation
 podpages_deps="perl"
 manpages_deps="perl pod2man"
-htmlpages_deps="texi2html"
-txtpages_deps="makeinfo"
+htmlpages_deps="perl texi2html"
+txtpages_deps="perl makeinfo"
 doc_deps_any="manpages htmlpages podpages txtpages"
 
 # default parameters

doc/Makefile

@@ -43,7 +43,7 @@ doc: documentation
 apidoc: doc/doxy/html
 documentation: $(DOCS)
 
-TEXIDEP = awk '/^@(verbatim)?include/ { printf "$@: $(@D)/%s\n", $$2 }' <$< >$(@:%=%.d)
+TEXIDEP = perl $(SRC_PATH)/doc/texidep.pl $< $@ >$(@:%=%.d)
 
 doc/%.txt: TAG = TXT
 doc/%.txt: doc/%.texi

doc/texidep.pl

@@ -0,0 +1,22 @@
+#! /usr/bin/perl
+
+use warnings;
+use strict;
+
+my ($root, $target) = @ARGV;
+
+sub print_deps {
+    my ($file, $deps) = @_;
+    $deps->{$file} = 1;
+
+    open(my $fh, "$file") or die "Cannot open file '$file': $!";
+    while (<$fh>) {
+        /^@(?:verbatim)?include\s+(\S+)/ and do {
+            die "Circular dependency found in file $root\n" if exists $deps->{"doc/$1"};
+            print "$target: doc/$1\n";
+            print_deps("doc/$1", {%$deps});
+        }
+    }
+}
+
+print_deps($root, {});