Add support for .ruby-variant

README.md

@@ -102,6 +102,14 @@ operating system will do the following:
 * Run the shim named `rake`, which in turn passes the command along to
   rbenv
 
+### .ruby-version and .ruby-variant
+
+Typically most projects will commit a `.ruby-version` file to their projects git repository. This causes conflicts when you are using a different variant of Ruby on the server. 
+
+For example, lets say that in development you have not installed fullstaq-rbenv and you have defined `2.6.3` in your `.ruby-version` file. On the server you have installed fullstaq-ruby and only installed `2.6.3-jemalloc`. Rbenv will complain that `2.6.3` is not installed as that is what your `.ruby-version` has defined.
+
+The solution to this is to add a `.ruby-variant` file to your project. For example if you are using the jemalloc variant simply put `jemalloc` in this file. Only when you are using fullstaq-rbenv will it combine the contents of `.ruby-version` and `.ruby-variant` to a single version string, ie. `2.6.3-jemalloc`.
+
 ### Choosing the Ruby Version
 
 When you execute a shim, rbenv determines which Ruby version to use by

libexec/rbenv-version-file-read

@@ -14,6 +14,21 @@ if [ -e "$VERSION_FILE" ]; then
   if [ "$version" = ".." ] || [[ $version == */* ]]; then
     echo "rbenv: invalid version in \`$VERSION_FILE'" >&2
   elif [ -n "$version" ]; then
+    variant_file=""
+
+    if [[ "$(basename "$VERSION_FILE")" == ".ruby-version" ]]; then
+      variant_file="$(dirname "$VERSION_FILE")/.ruby-variant"
+    fi
+
+    if [[ -e "$variant_file" ]]; then
+      variant_words=( $(cat "$variant_file") )
+      variant="${variant_words[0]}"
+
+      if [ -n "$variant" ] && [[ "$version" != *-$variant ]]; then
+        version="${version}-${variant}"
+      fi
+    fi
+
     echo "$version"
     exit
   fi

test/version-file-read.bats

@@ -86,3 +86,25 @@ IN
   run rbenv-version-file-read my-version
   assert_failure "rbenv: invalid version in \`my-version'"
 }
+
+@test "appends text from .ruby-variant file" {
+  echo "2.6.3" > .ruby-version
+  echo "jemalloc" > .ruby-variant
+
+  run rbenv-version-file-read .ruby-version
+  assert_success "2.6.3-jemalloc"
+
+  rm .ruby-variant
+  echo "jemalloc malloctrim" > .ruby-variant
+
+  run rbenv-version-file-read .ruby-version
+  assert_success "2.6.3-jemalloc"
+}
+
+@test "doesnt append .ruby-variant if .ruby-version contains variant" {
+  echo "2.6.3-jemalloc" > .ruby-version
+  echo "jemalloc" > .ruby-variant
+
+  run rbenv-version-file-read .ruby-version
+  assert_success "2.6.3-jemalloc"
+}