fix: space-delimit target_branches input

Originally, I went for comma-separated values in the target_branches
input. However, commas are a valid char in git branchnames.

I think it makes more sense to delimit the values on spaces. Spaces are
not allowed in branchnames.

README.md

@@ -167,7 +167,7 @@ Please refer to this action's README for all available [placeholders](#placehold
 
 Default: `''` (disabled)
 
-The action will backport the pull request to each specified target branch (comma-separated).
+The action will backport the pull request to each specified target branch (space-delimited).
 See [How it works](#how-it-works).
 
 Can be used in addition to backport labels.

action.yml

@@ -42,7 +42,7 @@ inputs:
       [Backport ${target_branch}] ${pull_title}
   target_branches:
     description: >
-      The action will backport the pull request to each specified target branch (comma-separated).
+      The action will backport the pull request to each specified target branch (space-delimited).
       Can be used in addition to backport labels.
       By default, only backport labels are used to specify the target branches.
 outputs:

src/backport.ts

@@ -369,7 +369,7 @@ export function findTargetBranches(
   const targetBranchesFromLabels = findTargetBranchesFromLabels(labels, config);
   const configuredTargetBranches =
     config.target_branches
-      ?.split(",")
+      ?.split(" ")
       .map((t) => t.trim())
       .filter((t) => t !== "") ?? [];
 

src/test/backport.test.ts

@@ -85,7 +85,7 @@ describe("find target branches", () => {
         findTargetBranches(
           {
             labels: { pattern: default_pattern },
-            target_branches: "release-1,another/target/branch",
+            target_branches: "release-1 another/target/branch",
           },
           []
         )