update: improve some edge cases.

- When running `brew update` and there’s been no changes from upstream
on any repositories there’s no need to call the (relatively) slow `brew
update-report` when we already know what it will say (“Already up-to
date.”).
- When any`git fetch`es fail then throw out an error at the end of the
output and produce a failing exit code (closes #65).

3 files changed, 45 insertions, 8 deletions

diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index 1d9822ae5..9339a63d9 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -70,7 +70,9 @@ module Homebrew
     end
 
     if !updated
-      puts "Already up-to-date." unless ARGV.include?("--preinstall")
+      if !ARGV.include?("--preinstall") && !ENV["HOMEBREW_UPDATE_FAILED"]
+        puts "Already up-to-date."
+      end
     elsif hub.empty?
       puts "No changes to formulae."
     else
@@ -81,6 +83,8 @@ module Homebrew
     end
 
     Tap.each(&:link_manpages)
+
+    Homebrew.failed = true if ENV["HOMEBREW_UPDATE_FAILED"]
   end
 
   private
diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index ba5ed2598..cff66f7b4 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -158,6 +158,10 @@ pull() {
     CURRENT_REVISION="$(read_current_revision)"
     export HOMEBREW_UPDATE_BEFORE"$TAP_VAR"="$INITIAL_REVISION"
     export HOMEBREW_UPDATE_AFTER"$TAP_VAR"="$CURRENT_REVISION"
+    if [[ "$INITIAL_REVISION" != "$CURRENT_REVISION" ]]
+    then
+      HOMEBREW_UPDATED="1"
+    fi
     if ! git merge-base --is-ancestor "$INITIAL_REVISION" "$CURRENT_REVISION"
     then
       odie "Your $DIR HEAD is not a descendant of $UPSTREAM_BRANCH!"
@@ -210,7 +214,13 @@ pull() {
       --strategy-option=ignore-all-space
   fi
 
-  export HOMEBREW_UPDATE_AFTER"$TAP_VAR"="$(read_current_revision)"
+  CURRENT_REVISION="$(read_current_revision)"
+  export HOMEBREW_UPDATE_AFTER"$TAP_VAR"="$CURRENT_REVISION"
+
+  if [[ "$INITIAL_REVISION" != "$CURRENT_REVISION" ]]
+  then
+    HOMEBREW_UPDATED="1"
+  fi
 
   trap '' SIGINT
 
@@ -301,6 +311,9 @@ EOS
   # kill all of subprocess on interrupt
   trap '{ pkill -P $$; wait; exit 130; }' SIGINT
 
+  local update_failed_file="$HOMEBREW_REPOSITORY/.git/UPDATE_FAILED"
+  rm -f "$update_failed_file"
+
   for DIR in "$HOMEBREW_REPOSITORY" "$HOMEBREW_LIBRARY"/Taps/*/*
   do
     [[ -d "$DIR/.git" ]] || continue
@@ -335,9 +348,11 @@ EOS
         git fetch --force "${QUIET_ARGS[@]}" origin \
           "refs/heads/$UPSTREAM_BRANCH:refs/remotes/origin/$UPSTREAM_BRANCH" 2>/dev/null
       else
-        git fetch --force "${QUIET_ARGS[@]}" origin \
-          "refs/heads/$UPSTREAM_BRANCH:refs/remotes/origin/$UPSTREAM_BRANCH" || \
-            odie "Fetching $DIR failed!"
+        if ! git fetch --force "${QUIET_ARGS[@]}" origin \
+          "refs/heads/$UPSTREAM_BRANCH:refs/remotes/origin/$UPSTREAM_BRANCH"
+        then
+          echo "Fetching $DIR failed!" >> "$update_failed_file"
+        fi
       fi
     ) &
   done
@@ -345,6 +360,13 @@ EOS
   wait
   trap - SIGINT
 
+  if [[ -f "$update_failed_file" ]]
+  then
+    onoe < "$update_failed_file"
+    rm -f "$update_failed_file"
+    export HOMEBREW_UPDATE_FAILED="1"
+  fi
+
   for DIR in "$HOMEBREW_REPOSITORY" "$HOMEBREW_LIBRARY"/Taps/*/*
   do
     [[ -d "$DIR/.git" ]] || continue
@@ -352,6 +374,13 @@ EOS
   done
 
   chdir "$HOMEBREW_REPOSITORY"
-  brew update-report "$@"
-  return $?
+
+  if [[ -n "$HOMEBREW_UPDATED" || -n "$HOMEBREW_UPDATE_FAILED" ]]
+  then
+    brew update-report "$@"
+    return $?
+  elif [[ -z "$HOMEBREW_UPDATE_PREINSTALL" ]]
+  then
+    echo "Already up-to-date."
+  fi
 }
diff --git a/Library/brew.sh b/Library/brew.sh
index 33f446503..76cb2f9e9 100644
--- a/Library/brew.sh
+++ b/Library/brew.sh
@@ -1,6 +1,6 @@
 HOMEBREW_VERSION="0.9.9"
 
-odie() {
+onoe() {
   if [[ -t 2 ]] # check whether stderr is a tty.
   then
     echo -ne "\033[4;31mError\033[0m: " >&2 # highlight Error with underline and red color
@@ -13,6 +13,10 @@ odie() {
   else
     echo "$*" >&2
   fi
+}
+
+odie() {
+  onoe "$@"
   exit 1
 }