man.vim: Fix tagfunc to respect b:man_default_sects

Also, kudos to @zsugabubus for fixing a related issue in #12417

This also prevents any sorting of the paths from man. We need to
respect the order we get from it otherwise you end up loading

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/share/man/man1/ls.1

on MacOS instead of /usr/share/man/man1/ls.1

runtime/autoload/man.vim

@@ -52,7 +52,7 @@ function! man#open_page(count, count1, mods, ...) abort
     let ref = a:2.'('.a:1.')'
   endif
   try
-    let [sect, name] = man#extract_sect_and_name_ref(ref)
+    let [sect, name] = s:extract_sect_and_name_ref(ref)
     if a:count ==# a:count1
       " v:count defaults to 0 which is a valid section, and v:count1 defaults to
       " 1, also a valid section. If they are equal, count explicitly set.
@@ -83,7 +83,7 @@ endfunction
 
 function! man#read_page(ref) abort
   try
-    let [sect, name] = man#extract_sect_and_name_ref(a:ref)
+    let [sect, name] = s:extract_sect_and_name_ref(a:ref)
     let path = s:verify_exists(sect, name)
     let [sect, name] = s:extract_sect_and_name_path(path)
     let page = s:get_page(path)
@@ -196,7 +196,7 @@ endfunction
 
 " attempt to extract the name and sect out of 'name(sect)'
 " otherwise just return the largest string of valid characters in ref
-function! man#extract_sect_and_name_ref(ref) abort
+function! s:extract_sect_and_name_ref(ref) abort
   if a:ref[0] ==# '-' " try ':Man -pandoc' with this disabled.
     throw 'manpage name cannot start with ''-'''
   endif
@@ -315,7 +315,7 @@ function! s:error(msg) abort
   echohl None
 endfunction
 
-" see man#extract_sect_and_name_ref on why tolower(sect)
+" see s:extract_sect_and_name_ref on why tolower(sect)
 function! man#complete(arg_lead, cmd_line, cursor_pos) abort
   let args = split(a:cmd_line)
   let cmd_offset = index(args, 'Man')
@@ -372,14 +372,26 @@ function! s:get_paths(sect, name, do_fallback) abort
   " callers must try-catch this, as some `man` implementations don't support `s:find_arg`
   try
     let mandirs = join(split(s:system(['man', s:find_arg]), ':\|\n'), ',')
-    return globpath(mandirs,'man?/'.a:name.'*.'.a:sect.'*', 0, 1)
+    let paths = globpath(mandirs, 'man?/'.a:name.'*.'.a:sect.'*', 0, 1)
+    try
+      " Prioritize the result from verify_exists as it obeys b:man_default_sects.
+      let first = s:verify_exists(a:sect, a:name)
+      let paths = filter(paths, 'v:val !=# first')
+      let paths = [first] + paths
+    catch
+    endtry
+    return paths
   catch
     if !a:do_fallback
       throw v:exception
     endif
 
-    " fallback to a single path, with the page we're trying to find
-    return [s:verify_exists(a:sect, a:name)]
+    " Fallback to a single path, with the page we're trying to find.
+    try
+      return [s:verify_exists(a:sect, a:name)]
+    catch
+      return []
+    endtry
   endtry
 endfunction
 
@@ -418,7 +430,7 @@ function! man#init_pager() abort
   " know the correct casing, cf. `man glDrawArraysInstanced`).
   let ref = substitute(matchstr(getline(1), '^[^)]\+)'), ' ', '_', 'g')
   try
-    let b:man_sect = man#extract_sect_and_name_ref(ref)[0]
+    let b:man_sect = s:extract_sect_and_name_ref(ref)[0]
   catch
     let b:man_sect = ''
   endtry
@@ -430,7 +442,7 @@ function! man#init_pager() abort
 endfunction
 
 function! man#goto_tag(pattern, flags, info) abort
-  let [l:sect, l:name] = man#extract_sect_and_name_ref(a:pattern)
+  let [l:sect, l:name] = s:extract_sect_and_name_ref(a:pattern)
 
   let l:paths = s:get_paths(l:sect, l:name, v:true)
   let l:structured = []
@@ -440,9 +452,6 @@ function! man#goto_tag(pattern, flags, info) abort
     let l:structured += [{ 'name': l:n, 'path': l:path }]
   endfor
 
-  " sort by relevance - exact matches first, then the previous order
-  call sort(l:structured, { a, b -> a.name ==? l:name ? -1 : b.name ==? l:name ? 1 : 0 })
-
   if &cscopetag
     " return only a single entry so we work well with :cstag (#11675)
     let l:structured = l:structured[:0]