Allow PRs to have more than 100 commits for check_dependent_project.sh (#94)

* allow PRs to have more than 100 commits

* add missing fetch

* fix exit code detection

* fix variable usage

* better var name

Author: joao-paulo-parity

check_dependent_project.sh

@@ -50,8 +50,44 @@ github_api="https://api.github.com"
 github_graphql_api="https://api.github.com/graphql"
 org_github_prefix="https://github.com/$org"
 org_crates_prefix="git+$org_github_prefix"
+# Heuristic: assume the companion PR has a common merge ancestor with master
+# in its last N commits.
+merge_ancestor_max_depth=256
 set +x
 
+merge_remote_ref() {
+  local remote="$1"
+  local ref="$2"
+  local repo="$3"
+  local pr_number="$4"
+  local message="$5"
+
+  git show-ref "$remote"/"$ref"
+
+  local merge_exit_code
+  git merge \
+    "$remote"/"$ref" \
+      --verbose \
+      --no-edit \
+      -m "$message" \
+    || merge_exit_code=$?
+
+  if [ "${merge_exit_code:-0}" != 0 ]; then
+    echo "
+Failed to merge $ref into $repo#$pr_number after fetching its last $merge_ancestor_max_depth commits.
+
+This problem can happen if:
+
+- $repo#$pr_number has conflicts with master. To solve this problem you should merge master into the PR, solve the conflicts and push.
+
+OR
+
+- $repo#$pr_number is ahead of master by more than $merge_ancestor_max_depth commits. To solve this you can merge master into the branch locally and push.
+"
+    exit $merge_exit_code
+  fi
+}
+
 our_crates=()
 discover_our_crates() {
   # workaround for early exits not being detected in command substitution
@@ -226,10 +262,6 @@ process_pr_description_line() {
 
     companions+=("$repo")
 
-    # Heuristic: assume the companion PR has a common merge ancestor with master
-    # in its last N commits.
-    local merge_ancestor_max_depth=100
-
     # Clone the default branch of this companion's target repository (assumed to
     # be named "master")
     git clone \
@@ -246,24 +278,12 @@ process_pr_description_line() {
     git fetch --depth=$merge_ancestor_max_depth origin "pull/$pr_number/head:$ref"
     git checkout "$ref"
 
-echo "
-Attempting to merge $repo#$pr_number with master after fetching its last $merge_ancestor_max_depth commits.
-
-If this step fails, either:
-
-- $repo#$pr_number has conflicts with master
-
-OR
-
-- A common merge ancestor could not be found between master and the last $merge_ancestor_max_depth commits of $repo#$pr_number.
-
-Both cases can be solved by merging master into $repo#$pr_number.
-"
-    git show-ref origin/master
-    git merge origin/master \
-      --verbose \
-      --no-edit \
-      -m "Merge master of $repo into companion $repo#$pr_number"
+    merge_remote_ref \
+      origin \
+      master \
+      "$repo" \
+      "$pr_number" \
+      "Merge master of $repo into companion $repo#$pr_number"
 
     popd >/dev/null
 
@@ -457,7 +477,10 @@ patch_and_check_dependent() {
 }
 
 main() {
-  if ! [[ "$CI_COMMIT_REF_NAME" =~ ^[[:digit:]]+$ ]]; then
+  local this_pr_number
+  if [[ "$CI_COMMIT_REF_NAME" =~ ^[[:digit:]]+$ ]]; then
+    this_pr_number="$CI_COMMIT_REF_NAME"
+  else
     die "\"$CI_COMMIT_REF_NAME\" was not recognized as a pull request ref"
   fi
 
@@ -469,7 +492,7 @@ main() {
   # process_pr_description calls itself for each companion in the description on
   # each detected companion PR, effectively considering all companion references
   # on all PRs
-  process_pr_description "$this_repo" "$CI_COMMIT_REF_NAME"
+  process_pr_description "$this_repo" "$this_pr_number"
 
   # This PR might be targetting a custom ref (i.e. not master) through companion
   # overrides from --companion-overrides or the PR's description, in which case
@@ -618,12 +641,12 @@ main() {
     # the same has to be done for all the companions because they might have
     # accompanying changes for the code being brought in.
     git fetch --force origin master
-    git show-ref origin/master
-    echo "Merge master into $this_repo#$CI_COMMIT_REF_NAME"
-    git merge origin/master \
-      --verbose \
-      --no-edit \
-      -m "Merge master into $this_repo#$CI_COMMIT_REF_NAME"
+    merge_remote_ref \
+      origin \
+      master \
+      "$this_repo" \
+      "$this_pr_number" \
+      "Merge master into $this_repo#$this_pr_number"
   fi
 
   discover_our_crates