Increase the minimum length for commit SHA matching to 7

This is the git default and will help to prevent false positive matches.

Closes #12706

app/models/commit.rb

@@ -68,18 +68,18 @@ class Commit
 
   # Pattern used to extract commit references from text
   #
-  # The SHA can be between 6 and 40 hex characters.
+  # The SHA can be between 7 and 40 hex characters.
   #
   # This pattern supports cross-project references.
   def self.reference_pattern
     %r{
       (?:#{Project.reference_pattern}#{reference_prefix})?
-      (?<commit>\h{6,40})
+      (?<commit>\h{7,40})
     }x
   end
 
   def self.link_reference_pattern
-    super("commit", /(?<commit>\h{6,40})/)
+    super("commit", /(?<commit>\h{7,40})/)
   end
 
   def to_reference(from_project = nil)

app/models/commit_range.rb

@@ -32,8 +32,8 @@ class CommitRange
   PATTERN = /#{REF_PATTERN}\.{2,3}#{REF_PATTERN}/
 
   # In text references, the beginning and ending refs can only be SHAs
-  # between 6 and 40 hex characters.
-  STRICT_PATTERN = /\h{6,40}\.{2,3}\h{6,40}/
+  # between 7 and 40 hex characters.
+  STRICT_PATTERN = /\h{7,40}\.{2,3}\h{7,40}/
 
   def self.reference_prefix
     '@'

config/routes.rb

@@ -490,7 +490,7 @@ Rails.application.routes.draw do
         end
 
         resource  :avatar, only: [:show, :destroy]
-        resources :commit, only: [:show], constraints: { id: /[[:alnum:]]{6,40}/ } do
+        resources :commit, only: [:show], constraints: { id: /\h{7,40}/ } do
           member do
             get :branches
             get :builds

spec/lib/banzai/filter/commit_reference_filter_spec.rb

@@ -21,7 +21,7 @@ describe Banzai::Filter::CommitReferenceFilter, lib: true do
     let(:reference) { commit.id }
 
     # Let's test a variety of commit SHA sizes just to be paranoid
-    [6, 8, 12, 18, 20, 32, 40].each do |size|
+    [7, 8, 12, 18, 20, 32, 40].each do |size|
       it "links to a valid reference of #{size} characters" do
         doc = reference_filter("See #{reference[0...size]}")
 
@@ -35,7 +35,7 @@ describe Banzai::Filter::CommitReferenceFilter, lib: true do
       doc = reference_filter("See #{commit.id}")
       expect(doc.text).to eq "See #{commit.short_id}"
 
-      doc = reference_filter("See #{commit.id[0...6]}")
+      doc = reference_filter("See #{commit.id[0...7]}")
       expect(doc.text).to eq "See #{commit.short_id}"
     end
 

spec/routing/project_routing_spec.rb

@@ -321,12 +321,12 @@ describe Projects::HooksController, 'routing' do
   end
 end
 
-# project_commit GET    /:project_id/commit/:id(.:format) commit#show {id: /[[:alnum:]]{6,40}/, project_id: /[^\/]+/}
+# project_commit GET    /:project_id/commit/:id(.:format) commit#show {id: /\h{7,40}/, project_id: /[^\/]+/}
 describe Projects::CommitController, 'routing' do
   it 'to #show' do
-    expect(get('/gitlab/gitlabhq/commit/4246fb')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fb')
-    expect(get('/gitlab/gitlabhq/commit/4246fb.diff')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fb', format: 'diff')
-    expect(get('/gitlab/gitlabhq/commit/4246fb.patch')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fb', format: 'patch')
+    expect(get('/gitlab/gitlabhq/commit/4246fbd')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fbd')
+    expect(get('/gitlab/gitlabhq/commit/4246fbd.diff')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fbd', format: 'diff')
+    expect(get('/gitlab/gitlabhq/commit/4246fbd.patch')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fbd', format: 'patch')
     expect(get('/gitlab/gitlabhq/commit/4246fbd13872934f72a8fd0d6fb1317b47b59cb5')).to route_to('projects/commit#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: '4246fbd13872934f72a8fd0d6fb1317b47b59cb5')
   end
 end

spec/support/filter_spec_helper.rb

@@ -67,9 +67,9 @@ module FilterSpecHelper
     if reference =~ /\A(.+)?.\d+\z/
       # Integer-based reference with optional project prefix
       reference.gsub(/\d+\z/) { |i| i.to_i + 1 }
-    elsif reference =~ /\A(.+@)?(\h{6,40}\z)/
+    elsif reference =~ /\A(.+@)?(\h{7,40}\z)/
       # SHA-based reference with optional prefix
-      reference.gsub(/\h{6,40}\z/) { |v| v.reverse }
+      reference.gsub(/\h{7,40}\z/) { |v| v.reverse }
     else
       reference.gsub(/\w+\z/) { |v| v.reverse }
     end