update: show message prompting brew tap --repair

This message is shown when a fetch fails due to a branch rename

Library/Homebrew/cmd/update-report.rb

@@ -144,6 +144,19 @@ module Homebrew
     link_completions_manpages_and_docs
     Tap.each(&:link_completions_and_manpages)
 
+    failed_fetch_dirs = ENV["HOMEBREW_FAILED_FETCH_DIRS"]&.split("\n")
+    if failed_fetch_dirs.present?
+      failed_fetch_taps = failed_fetch_dirs.map { |dir| Tap.from_path(dir) }
+
+      puts Formatter.headline "Some taps failed to update!", color: :red
+      puts <<~EOS
+        The following taps can not read their remote branches:
+          #{failed_fetch_taps.join("\n  ")}
+        This may be happening because the remote branch was renamed.
+        Reset taps to point to the correct remote branches by running `brew tap --repair`
+      EOS
+    end
+
     return if new_repository_version.blank?
 
     ohai "Homebrew was updated to version #{new_repository_version}"

Library/Homebrew/cmd/update-reset.sh

@@ -1,6 +1,6 @@
 #:  * `update-reset` [<repository> ...]
 #:
-#:  Fetch and reset Homebrew and all tap repositories (or any specified <repository>) using `git`(1) to their latest `origin/master`.
+#:  Fetch and reset Homebrew and all tap repositories (or any specified <repository>) using `git`(1) to their latest `origin/HEAD`.
 #:
 #:  *Note:* this will destroy all your uncommitted or committed changes.
 

Library/Homebrew/cmd/update.sh

@@ -483,7 +483,9 @@ EOS
   trap '{ /usr/bin/pkill -P $$; wait; exit 130; }' SIGINT
 
   local update_failed_file="$HOMEBREW_REPOSITORY/.git/UPDATE_FAILED"
+  local failed_fetch_dirs_file="$HOMEBREW_REPOSITORY/.git/FAILED_FETCH_DIRS"
   rm -f "$update_failed_file"
+  rm -f "$failed_fetch_dirs_file"
 
   for DIR in "$HOMEBREW_REPOSITORY" "$HOMEBREW_LIBRARY"/Taps/*/*
   do
@@ -566,23 +568,38 @@ EOS
         echo "Fetching $DIR..."
       fi
 
+      local tmp_failure_file="$HOMEBREW_REPOSITORY/.git/TMP_FETCH_FAILURES"
+      rm -f "$tmp_failure_file"
+
       if [[ -n "$HOMEBREW_UPDATE_PREINSTALL" ]]
       then
         git fetch --tags --force "${QUIET_ARGS[@]}" origin \
           "refs/heads/$UPSTREAM_BRANCH_DIR:refs/remotes/origin/$UPSTREAM_BRANCH_DIR" 2>/dev/null
       else
+        # Capture stderr to tmp_failure_file
         if ! git fetch --tags --force "${QUIET_ARGS[@]}" origin \
-          "refs/heads/$UPSTREAM_BRANCH_DIR:refs/remotes/origin/$UPSTREAM_BRANCH_DIR"
+          "refs/heads/$UPSTREAM_BRANCH_DIR:refs/remotes/origin/$UPSTREAM_BRANCH_DIR" 2>>"$tmp_failure_file"
         then
+          # Reprint fetch errors to stderr
+          [[ -f "$tmp_failure_file" ]] && cat "$tmp_failure_file" 1>&2
+
           if [[ "$UPSTREAM_SHA_HTTP_CODE" = "404" ]]
           then
             TAP="${DIR#$HOMEBREW_LIBRARY/Taps/}"
             echo "$TAP does not exist! Run \`brew untap $TAP\` to remove it." >>"$update_failed_file"
           else
             echo "Fetching $DIR failed!" >>"$update_failed_file"
+
+            if [[ -f "$tmp_failure_file" ]] &&
+               [[ "$(<"$tmp_failure_file")" = "fatal: couldn't find remote ref refs/heads/$UPSTREAM_BRANCH_DIR" ]]
+            then
+              echo "$DIR" >>"$failed_fetch_dirs_file"
             fi
           fi
         fi
+      fi
+
+      rm -f "$tmp_failure_file"
     ) &
   done
 
@@ -596,6 +613,13 @@ EOS
     export HOMEBREW_UPDATE_FAILED="1"
   fi
 
+  if [[ -f "$failed_fetch_dirs_file" ]]
+  then
+    HOMEBREW_FAILED_FETCH_DIRS="$(<"$failed_fetch_dirs_file")"
+    rm -f "$failed_fetch_dirs_file"
+    export HOMEBREW_FAILED_FETCH_DIRS
+  fi
+
   for DIR in "$HOMEBREW_REPOSITORY" "$HOMEBREW_LIBRARY"/Taps/*/*
   do
     [[ -d "$DIR/.git" ]] || continue
@@ -629,6 +653,7 @@ EOS
 
   if [[ -n "$HOMEBREW_UPDATED" ||
         -n "$HOMEBREW_UPDATE_FAILED" ||
+        -n "$HOMEBREW_FAILED_FETCH_DIRS" ||
         -n "$HOMEBREW_UPDATE_FORCE" ||
         -d "$HOMEBREW_LIBRARY/LinkedKegs" ||
         ! -f "$HOMEBREW_CACHE/all_commands_list.txt" ||

completions/zsh/_brew

@@ -217,7 +217,7 @@ __brew_internal_commands() {
     'update-license-data:Update SPDX license data in the Homebrew repository'
     'update-python-resources:Update versions for PyPI resource blocks in formula'
     'update-report:The Ruby implementation of `brew update`'
-    'update-reset:Fetch and reset Homebrew and all tap repositories (or any specified repository) using `git`(1) to their latest `origin/master`'
+    'update-reset:Fetch and reset Homebrew and all tap repositories (or any specified repository) using `git`(1) to their latest `origin/HEAD`'
     'update-test:Run a test of `brew update` with a new repository clone'
     'upgrade:Upgrade outdated casks and outdated, unpinned formulae using the same options they were originally installed with, plus any appended brew formula options'
     'uses:Show formulae and casks that specify formula as a dependency; that is, show dependents of formula'

docs/Manpage.md

@@ -607,7 +607,7 @@ Fetch the newest version of Homebrew and all formulae from GitHub using `git`(1)
 
 ### `update-reset` [*`repository`* ...]
 
-Fetch and reset Homebrew and all tap repositories (or any specified *`repository`*) using `git`(1) to their latest `origin/master`.
+Fetch and reset Homebrew and all tap repositories (or any specified *`repository`*) using `git`(1) to their latest `origin/HEAD`.
 
 *Note:* this will destroy all your uncommitted or committed changes.
 

manpages/brew.1

@@ -812,7 +812,7 @@ Run on auto\-updates (e\.g\. before \fBbrew install\fR)\. Skips some slower step
 Always do a slower, full update check (even if unnecessary)\.
 .
 .SS "\fBupdate\-reset\fR [\fIrepository\fR \.\.\.]"
-Fetch and reset Homebrew and all tap repositories (or any specified \fIrepository\fR) using \fBgit\fR(1) to their latest \fBorigin/master\fR\.
+Fetch and reset Homebrew and all tap repositories (or any specified \fIrepository\fR) using \fBgit\fR(1) to their latest \fBorigin/HEAD\fR\.
 .
 .P
 \fINote:\fR this will destroy all your uncommitted or committed changes\.