From 800e8ba4da76590c8cbe9801bef49a7ffb30bfbc Mon Sep 17 00:00:00 2001
From: "Joshua C. Randall" <jcrandall@alum.mit.edu>
Date: Fri, 31 Jul 2015 02:00:28 +0100
Subject: [PATCH] Adds useful log warnings re: repo failures

Instruments the find_commit_range function such that it logs an
explanatory warning in any case when it fails to find any refs.

When no refs are found, find_commit_range returns an empty list
which typically causes its caller to throw an exception. Without
these added warnings, that exception is not at all helpful in
tracking down the underlying issue.
---
 services/api/app/models/commit.rb | 32 +++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/services/api/app/models/commit.rb b/services/api/app/models/commit.rb
index a6b085722e..e4b789e099 100644
--- a/services/api/app/models/commit.rb
+++ b/services/api/app/models/commit.rb
@@ -58,12 +58,22 @@ class Commit < ActiveRecord::Base
 
     # Get the commit hash for the upper bound
     max_hash = nil
-    IO.foreach("|git rev-list --max-count=1 #{maximum.shellescape} --") do |line|
+    git_max_hash_cmd = "git rev-list --max-count=1 #{maximum.shellescape} --"
+    IO.foreach("|#{git_max_hash_cmd}") do |line|
       max_hash = line.strip
     end
 
-    # If not found or string is invalid, nothing else to do
-    return [] if !max_hash or !git_check_ref_format(max_hash)
+    # If not found, nothing else to do
+    if !max_hash
+      logger.warn "no refs found looking for max_hash: `GIT_DIR=#{gitdir} #{git_max_hash_cmd}` returned no output"
+      return []
+    end
+
+    # If string is invalid, nothing else to do
+    if !git_check_ref_format(max_hash)
+      logger.warn "ref returned by `GIT_DIR=#{gitdir} #{git_max_hash_cmd}` was invalid for max_hash: #{max_hash}"
+      return[]
+    end
 
     resolved_exclude = nil
     if exclude
@@ -83,12 +93,22 @@ class Commit < ActiveRecord::Base
     if minimum
       # Get the commit hash for the lower bound
       min_hash = nil
-      IO.foreach("|git rev-list --max-count=1 #{minimum.shellescape} --") do |line|
+      git_min_hash_cmd = "git rev-list --max-count=1 #{minimum.shellescape} --"
+      IO.foreach("|#{git_min_hash_cmd}") do |line|
         min_hash = line.strip
       end
 
-      # If not found or string is invalid, nothing else to do
-      return [] if !min_hash or !git_check_ref_format(min_hash)
+      # If not found, nothing else to do
+      if !min_hash
+        logger.warn "no refs found looking for min_hash: `GIT_DIR=#{gitdir} #{git_min_hash_cmd}` returned no output"
+        return []
+      end
+
+      # If string is invalid, nothing else to do
+      if !git_check_ref_format(min_hash)
+        logger.warn "ref returned by `GIT_DIR=#{gitdir} #{git_min_hash_cmd}` was invalid for min_hash: #{min_hash}"
+        return []
+      end
 
       # Now find all commits between them
       IO.foreach("|git rev-list #{min_hash.shellescape}..#{max_hash.shellescape} --") do |line|
-- 
2.39.5