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.

diff --git a/services/api/app/models/commit.rb b/services/api/app/models/commit.rb
index a6b085722e90fb043a2277f7781727218e8e2559..e4b789e099abb24c3618cd290d81a3200b597d42 100644 (file)
--- 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|