Add completions for mkvextract (#3492)

* add completions for mkvextract

* fix edge cases with option placement in mkvextract.fish

* improve resiliency to errors in mkvextract.fish

* minor fixes in mkvextract.fish

share/completions/mkvextract.fish

@@ -0,0 +1,82 @@
+# Sample output of 'mkvmerge -i file.mkv'
+# 
+# File 'file.mkv': container: Matroska
+# Track ID 0: video (MPEG-4p10/AVC/h.264)
+# Track ID 1: audio (AAC)
+# Track ID 2: subtitles (SubStationAlpha)
+# Attachment ID 1: type 'application/x-truetype-font', size 53532 bytes, file name 'some_font.ttf'
+# Chapters: 7 entires
+
+function __fish_mkvextract_find_matroska_in_args
+    set -l cmd (commandline -opc)
+    if not set -q cmd[3]
+        return 1
+    end
+    for c in $cmd[3..-1]
+        set -l skip_next 1
+        test $skip_next -eq 0; and set skip_next 1; and continue
+        switch $c
+            # General options with an argument we need to skip
+            case "--ui-language" "--command-line-charset" "--output-charset" "-r" "--redirect-output" "-c" "--blockadd" "--simple-language"
+                set skip_next 0
+                continue
+            # these behave like commands and everything after them is ignored
+            case "-h" "--help" "-V" "--version"
+                return 1
+            case "*"
+                if test -f "$c"
+                    echo $c
+                    return 0
+                end
+                continue
+        end
+    end
+    return 1
+end
+
+function __fish_mkvextract_print_attachments
+    if set -l matroska (__fish_mkvextract_find_matroska_in_args)
+        if set -l info (mkvmerge -i $matroska)
+            string match 'Attachment ID*' -- $info | string replace -r '.*?(\d+).*? type \'(.*?)\'.*?file name \'(.*?)\'' '$1:\t$3 ($2)'
+        end
+    end
+end
+
+function __fish_mkvextract_print_tracks
+    if set -l matroska (__fish_mkvextract_find_matroska_in_args)
+        if set -l info (mkvmerge -i $matroska)
+            string match 'Track ID*' -- $info | string replace -r '.*?(\d+): (.*)' '$1:\t$2'
+        end
+    end
+end
+
+# simple options
+complete -f -c mkvextract -s V -l "version" -d "Show version information"
+complete -f -c mkvextract -s h -l "help"    -d "Show help"
+# commands
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "tracks"       -d "Extract tracks to external files"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "tags"         -d "Extract tags as XML"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "attachments"  -d "Extract attachments"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "chapters"     -d "Extract chapters as XML"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "cuesheet"     -d "Extract chapters and tags as CUE sheet"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "timecodes_v2" -d "Extract timecodes of a track as timecode v2 file"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -lt 2" -a "cues"         -d "Extract cue information as text file"
+# dynamic tracks and attachments completions
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks timecodes_v2 cues" -a "(__fish_mkvextract_print_tracks)"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from attachments"              -a "(__fish_mkvextract_print_attachments)"
+# options common to all commands
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2"    -s f -l "parse-fully"          -d "Parse the whole file instead of relying on the index"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2"    -s v -l "verbose"              -d "Increase verbosity"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2"    -s q -l "quiet"                -d "Suppress status output"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2" -r      -l "ui-language"          -d "Force the translations for 'code' to be used"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2" -r      -l "command-line-charset" -d "Charset for strings on the command line"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2" -r      -l "output-charset"       -d "Outputs messages in specified charset"
+complete -f -c mkvextract -n "test (count (commandline -opc)) -ge 2" -r -s r -l "redirect-output"      -d "Redirect all messages into a file"
+# command-specific options
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks"   -r -s c                      -d "Convert text subtitles to a charset"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks"           -l "cuesheet"        -d "Also try to extract the CUE sheet"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks"   -r      -l "blockadd"        -d "Keep only the BlockAdditions up to the specified level"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks"           -l "raw"             -d "Extract the data to a raw file"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from tracks"           -l "fullraw"         -d "Extract the data to a raw file including the CodecPrivate as header"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from chapters"    -s s -l "simple"          -d "Exports the chapter information in a simple format"
+complete -f -c mkvextract -n "__fish_seen_subcommand_from chapters" -r      -l "simple-language" -d "Uses the chapter names of the specified language"