Make mysql completions work with log-in (#7397)

Complete databases using credentials specified on the commandline.

share/completions/mysql.fish

@@ -1,3 +1,5 @@
+__fish_complete_mysql mysql
+
 complete -c mysql -f
 
 complete -c mysql -s I -s \? -l help -d 'Display a help message'
@@ -13,8 +15,7 @@ complete -c mysql -s c -l comments -d 'Preserve comments in statements'
 complete -c mysql -l skip-comments -d 'Discard comments in statements'
 complete -c mysql -s C -l compress -d 'Compress all information'
 complete -c mysql -l connect-timeout -x -d 'Set the number of seconds before connection timeout'
-complete -c mysql -s D -l database -x -d 'The database to use' -a '(mysqlshow 2>/dev/null | tail -n +3 | string replace -rf \'\| *(\S*) *\|\' \'$1\')'
-complete -c mysql -a '(mysqlshow 2>/dev/null | tail -n +3 | string replace -rf \'\| *(\S*) *\|\' \'$1\')'
+
 complete -c mysql -s \# -l debug -d 'Write a debugging log'
 complete -c mysql -l debug-check -d 'Print some debugging information'
 complete -c mysql -s T -l debug-info -d 'Prints debugging information and memory and CPU usage'

share/completions/mysqldump.fish

@@ -0,0 +1 @@
+__fish_complete_mysql mysqldump

share/functions/__fish_complete_mysql.fish

@@ -0,0 +1,25 @@
+function __fish_mysql_query -a query
+    argparse -i 'u/user=' 'P/port=' 'h/host=' 'p/password=?' 'S/socket=' -- (commandline -po)
+    set -l mysql_cmd mysql
+    for flag in u P h S
+        if set -q _flag_$flag
+            set -l flagvar _flag_$flag
+            set -a mysql_cmd -$flag $$flagvar
+        end
+    end
+    if [ -n "$_flag_p" ]
+        set -a mysql_cmd -p$_flag_p
+    end
+    echo $query | $mysql_cmd 2>/dev/null
+end
+
+function __fish_complete_mysql_databases
+    __fish_mysql_query 'show databases'
+end
+
+function __fish_complete_mysql
+    set -l command $argv[1]
+
+    complete -c $command -s D -l database -x -d 'The database to use' -a '(__fish_complete_mysql_databases)'
+    complete -c $command -a '(__fish_complete_mysql_databases)'
+end