feat(tests): add reusable script to apply upstream branch

Add a new helper script (apply-upstream-branch.sh) used by Playwright
e2e tests to apply a remote branch into a cloned test workspace. The
script prints environment debug info, accepts branch and directory
arguments, and runs the stack-branches command with -u for upstream
applies.

Introduce project-with-stacks.sh to create a remote git repo with
multiple independent branches and clone it into local-clone. This
replaces and consolidates previous test setup logic.

Update tests (branches.spec.ts) to call the new apply-upstream-branch
script with explicit branch and directory parameters instead of the
removed project-with-remote-branches__apply-branch-1.sh script.

Remove obsolete project-with-remote-branches__apply-branch-1.sh. The
changes make branch application reusable and parameterized, improving
test clarity and reducing duplication.

Author: estib-vega

e2e/playwright/scripts/apply-upstream-branch.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+echo "GIT CONFIG $GIT_CONFIG_GLOBAL"
+echo "DATA DIR $GITBUTLER_CLI_DATA_DIR"
+echo "BUT_TESTING $BUT_TESTING"
+echo "BRANCH TO APPLY: $1"
+echo "DIRECTORY: $2"
+
+# Apply remote branch to the workspace.
+pushd "$2"
+  $BUT_TESTING -j stack-branches -u -b $1
+popd

e2e/playwright/scripts/project-with-remote-branches__apply-branch-1.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+
+echo "GIT CONFIG $GIT_CONFIG_GLOBAL"
+echo "DATA DIR $GITBUTLER_CLI_DATA_DIR"
+echo "BUT_TESTING $BUT_TESTING"
+
+# Setup a remote project.
+# GitButler currently requires projects to have a remote
+mkdir remote-project
+pushd remote-project
+git init -b master --object-format=sha1
+echo "foo" >> a_file
+echo "bar" >> a_file
+echo "baz" >> a_file
+git add a_file
+git commit -am "Hey, look! A commit."
+
+# Create branch 1
+git checkout -b branch1
+echo "branch1 commit 1" >> a_file
+git commit -am "branch1: first commit"
+echo "branch1 commit 2" >> a_file
+git commit -am "branch1: second commit"
+echo "branch1 commit 1" >> a_file
+git commit -am "branch1: third commit"
+echo "branch1 commit 2" >> a_file
+git commit -am "branch1: fourth commit"
+git checkout master
+
+# Create branch 2
+# Branch 2 is independent
+git checkout -b branch2
+echo "branch2 commit 1" >> b_file
+git add b_file
+git commit -am "branch2: first commit"
+echo "branch2 commit 2" >> b_file
+git commit -am "branch2: second commit"
+git checkout master
+
+# Create branch 3, also independent
+git checkout -b branch3
+echo "branch3 commit 1" >> c_file
+git add c_file
+git commit -am "branch3: first commit"
+echo "branch3 commit 2" >> c_file
+git commit -am "branch3: second commit"
+git checkout master
+popd
+
+# Clone the remote into a folder and add the project to the application.
+git clone remote-project local-clone
+pushd local-clone
+  git checkout master
+  $BUT_TESTING add-project --switch-to-workspace "$(git rev-parse --symbolic-full-name @{u})"
+popd

e2e/playwright/scripts/project-with-stacks.sh

@@ -137,7 +137,7 @@ test('should be able to apply a remote branch and integrate the remote changes -
 	const fileCPath = gitbutler.pathInWorkdir('local-clone/c_file');
 
 	await gitbutler.runScript('project-with-remote-branches.sh');
-	await gitbutler.runScript('project-with-remote-branches__apply-branch-1.sh');
+	await gitbutler.runScript('apply-upstream-branch.sh', ['branch1', 'local-clone']);
 
 	await page.goto('/');
 
@@ -197,7 +197,7 @@ test('should be able to apply a remote branch and integrate the remote changes -
 	const filePath = gitbutler.pathInWorkdir('local-clone/a_file');
 
 	await gitbutler.runScript('project-with-remote-branches.sh');
-	await gitbutler.runScript('project-with-remote-branches__apply-branch-1.sh');
+	await gitbutler.runScript('apply-upstream-branch.sh', ['branch1', 'local-clone']);
 
 	await page.goto('/');
 
@@ -543,7 +543,7 @@ test('should handle gracefully applying two conflicting branches', async ({
 	gitbutler = await startGitButler(workdir, configdir, context);
 
 	await gitbutler.runScript('project-with-remote-branches.sh');
-	await gitbutler.runScript('project-with-remote-branches__apply-branch-1.sh');
+	await gitbutler.runScript('apply-upstream-branch.sh', ['branch1', 'local-clone']);
 
 	await page.goto('/');