Add bash completion script

Signed-off-by: Phil Dibowitz <phil@ipom.com>

README.md

@@ -415,3 +415,9 @@ will allow me to make sure it shows up in the Repology badge above.
 Since it's Ruby, it should work across all platforms, however, it's developed
 and primarily tested on Linux as well as regularly used on Mac. I've not tested
 it on Windows, but I'll happily accept patches for Windows compatibility.
+
+**How do I get tab-completion?**
+
+If the package for your OS/distro didn't set it up manually, you should find
+that `sugarjar_completion.bash` is included in the package, and you can simply
+source that in your dotfiles, assuming you are using bash.

extras/sugarjar_completion.bash

@@ -0,0 +1,42 @@
+# bash completion for sugarjar
+
+SJCONFIG="$HOME/.config/sugarjar/config.yaml"
+
+_sugarjar_completions()
+{
+    if [ "${#COMP_WORDS[@]}" -eq 2 ]; then
+        return
+    fi
+
+    local -a suggestions
+
+    # grap the feature_prefix if we have one so that we
+    # can let the user ignore that part. If we have `yq`
+    # we'll use it as that's going to be always 100%
+    # reliable, but if we don't, do our best with shell
+    # utils
+    local prefix=''
+    if [ -e "$SJCONFIG" ]; then
+        if type yq &>/dev/null; then
+            prefix=$(yq .feature_prefix $SJCONFIG)
+        else
+            # the xargs removes extra spaces
+            prefix=$(grep feature_prefix $SJCONFIG | cut -f2 -d: | xargs)
+        fi
+    fi
+
+    case "${COMP_WORDS[1]}" in
+        co|checkout|bclean)
+            local branches=$(git branch | sed -e 's/* //g' | xargs)
+            if [ -n "$prefix" ]; then
+                local branches=$(echo $branches | sed -e "s!$prefix!!g")
+            fi
+            suggestions=($(compgen -W "$branches" -- "${COMP_WORDS[2]}"))
+            COMPREPLY=("${suggestions[@]}")
+            ;;
+        *)
+            return
+    esac
+}
+
+complete -F _sugarjar_completions sj

sugarjar.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |spec|
   spec.files =
     Dir.glob('lib/sugarjar/*.rb') +
     Dir.glob('bin/*') +
-    docs
+    Dir.glob('extras/*')
 
   spec.add_dependency 'deep_merge'
   spec.add_dependency 'mixlib-log'