Support arbitrary object name lengths (set with core.abbrev)

Support core.abbrev set to non-default values between 4 and 40.

We ran into an issue when we bumped to Ubuntu 18 (bionic) and started seeing failures in process_full_diff because the index lines had 11 character SHA abbreviations. This should allow core.abbrev to be set to anything between 4 (the min) and 40 (the max).

Signed-off-by: Nicholas Calugar <nicholas.calugar@gusto.com>
Co-authored-by: Ngan Pham <ngan@users.noreply.github.com>

lib/git/diff.rb

@@ -72,6 +72,7 @@ def each(&block) # :yields: each Git::DiffFile in turn
     class DiffFile
       attr_accessor :patch, :path, :mode, :src, :dst, :type
       @base = nil
+      NIL_BLOB_REGEXP = /\A0{4,40}\z/.freeze
 
       def initialize(base, hash)
         @base = base
@@ -89,10 +90,10 @@ def binary?
       end
 
       def blob(type = :dst)
-        if type == :src
-          @base.object(@src) if @src != '0000000'
-        else
-          @base.object(@dst) if @dst != '0000000'
+        if type == :src && !NIL_BLOB_REGEXP.match(@src)
+          @base.object(@src)
+        elsif !NIL_BLOB_REGEXP.match(@dst)
+          @base.object(@dst)
         end
       end
     end
@@ -132,7 +133,7 @@ def process_full_diff
             current_file = m[1]
             final[current_file] = defaults.merge({:patch => line, :path => current_file})
           else
-            if m = /^index (.......)\.\.(.......)( ......)*/.match(line)
+            if m = /^index ([0-9a-f]{4,40})\.\.([0-9a-f]{4,40})( ......)*/.match(line)
               final[current_file][:src] = m[1]
               final[current_file][:dst] = m[2]
               final[current_file][:mode] = m[3].strip if m[3]

tests/units/test_diff.rb

@@ -76,11 +76,31 @@ def test_diff_stats
     assert_equal(1, s[:files]["scott/newfile"][:deletions])
   end
 
-  def test_diff_hashkey
+  def test_diff_hashkey_default
     assert_equal('5d46068', @diff["scott/newfile"].src)
     assert_nil(@diff["scott/newfile"].blob(:dst))
     assert(@diff["scott/newfile"].blob(:src).is_a?(Git::Object::Blob))
   end
+
+  def test_diff_hashkey_min
+    set_file_paths
+    git = Git.open(@wdir)
+    git.config('core.abbrev', 4)
+    diff = git.diff('gitsearch1', 'v2.5')
+    assert_equal('5d46', diff["scott/newfile"].src)
+    assert_nil(diff["scott/newfile"].blob(:dst))
+    assert(diff["scott/newfile"].blob(:src).is_a?(Git::Object::Blob))
+  end
+
+  def test_diff_hashkey_max
+    set_file_paths
+    git = Git.open(@wdir)
+    git.config('core.abbrev', 40)
+    diff = git.diff('gitsearch1', 'v2.5')
+    assert_equal('5d4606820736043f9eed2a6336661d6892c820a5', diff["scott/newfile"].src)
+    assert_nil(diff["scott/newfile"].blob(:dst))
+    assert(diff["scott/newfile"].blob(:src).is_a?(Git::Object::Blob))
+  end
 
   def test_patch
     p = @git.diff('v2.8^', 'v2.8').patch