etc: make the new bash-completion file work for all variants of our executables.

In particular make it also work with the `gimp-console` and with all
symlink names.

Also rename the bash completion file using the full application version
so that it will be possible to install several such completion files
side by side.

etc/bash_completion.in

@@ -0,0 +1,90 @@
+__gimp()
+{
+    COMPREPLY=()
+    local current="${COMP_WORDS[COMP_CWORD]}"
+    local prev="${COMP_WORDS[COMP_CWORD-1]}"
+
+    # GIMP options, sorted alphabetically
+    #
+    # Note that we don't specify short options here, since they're quite unintuitive
+    options=(
+        "--as-new"
+        "--batch"
+        "--batch-interpreter"
+        "--console-messages"
+        "--debug-handlers"
+        "--dump-gimprc"
+        "--dump-gimprc-manpage"
+        "--dump-gimprc-system"
+        "--dump-pdb-procedures-deprecated"
+        "--g-fatal-warnings"
+        "--gimprc"
+        "--help"
+        "--help-all"
+        "--help-gegl"
+        "--help-gtk"
+        "--license"
+        "--new-instance"
+        "--no-cpu-accel"
+        "--no-data"
+        "--no-fonts"
+        "--no-interface"
+        "--no-shm"
+        "--no-splash"
+        "--pdb-compat-mode"
+        "--session"
+        "--show-playground"
+        "--stack-trace-mode"
+        "--system-gimprc"
+        "--verbose"
+        "--version"
+    )
+
+    #
+    # Different completions for specific options
+    #
+    case "${prev}" in
+        # Options that shouldn't be used in combination with something else
+        help | license | version)
+            return 0
+            ;;
+        # Expect a filename
+        gimprc | session | system-gimprc)
+            COMPREPLY=( $(compgen -f -- ${current}) )
+            return 0
+            ;;
+        # Expect *some* argument, so don't complete
+        b | batch | display)
+            return 0
+            ;;
+        batch-interpreter)
+            # FIXME: we should try to get the list of interpreters somehow
+            local interpreters=$(gimp --LIST_INTERPRETERS)
+            COMPREPLY=("python-fu-eval" "plug-in-script-fu-eval")
+            return 0
+            ;;
+        *)
+        ;;
+    esac
+
+   # Default: complete with either an option "-W" or a filename "-f"
+   COMPREPLY=($(compgen -W "${options[*]}" -f -- ${current}))
+   return 0
+}
+
+complete -F __gimp @GIMP_MAIN_EXE@
+if command -v @GIMP_SYMLINK1@ 2>&1 > /dev/null
+then
+  complete -F __gimp @GIMP_SYMLINK1@
+  complete -F __gimp @GIMP_SYMLINK2@
+fi
+
+if command -v @GIMP_CONSOLE_EXE@ 2>&1 > /dev/null
+then
+  complete -F __gimp @GIMP_CONSOLE_EXE@
+  if command -v @GIMP_CONSOLE_SYMLINK1@ 2>&1 > /dev/null
+  then
+    complete -F __gimp @GIMP_CONSOLE_SYMLINK1@
+    complete -F __gimp @GIMP_CONSOLE_SYMLINK2@
+  fi
+fi

etc/meson.build

@@ -19,3 +19,35 @@ install_data(
   ],
   install_dir: gimpsysconfdir,
 )
+
+# Bash completion
+have_bash = find_program('bash', required : false).found() # For completion scripts
+bash_comp_dep = dependency('bash-completion', version: '>=2.0', required: false)
+if have_bash
+
+  bash_comp_inst_dir = ''
+  if bash_comp_dep.found()
+    bash_comp_dir_override = bash_comp_dep.version().version_compare('>= 2.10') ? ['datadir', get_option('datadir')] : ['prefix', get_option('prefix')]
+    bash_comp_inst_dir = bash_comp_dep.get_variable('completionsdir', pkgconfig_define: bash_comp_dir_override)
+  endif
+
+  if bash_comp_inst_dir == ''
+    message('Found bash-completion but the .pc file did not set \'completionsdir\', fallback to a predefined path')
+    bash_comp_inst_dir = get_option('datadir') / 'bash-completion' / 'completions'
+  endif
+
+  bash_completion_conf = configuration_data()
+  bash_completion_conf.set('GIMP_MAIN_EXE', gimpmain_exe_name)
+  bash_completion_conf.set('GIMP_SYMLINK1', 'gimp-' + gimp_app_version_major.to_string())
+  bash_completion_conf.set('GIMP_SYMLINK2', 'gimp')
+
+  bash_completion_conf.set('GIMP_CONSOLE_EXE',      gimpconsole_exe_name)
+  bash_completion_conf.set('GIMP_CONSOLE_SYMLINK1', 'gimp-console-' + gimp_app_version_major.to_string())
+  bash_completion_conf.set('GIMP_CONSOLE_SYMLINK2', 'gimp-console')
+
+  configure_file(input : 'bash_completion.in',
+                 output: 'gimp-' + gimp_app_version,
+                 configuration: bash_completion_conf,
+                 install: true,
+                 install_dir: bash_comp_inst_dir)
+endif