From c6ed14c6622ff8e319fd627c6a1c26668d9ff730 Mon Sep 17 00:00:00 2001
From: Andy Stewart <boss@airbladesoftware.com>
Date: Thu, 5 Mar 2015 10:17:38 +0100
Subject: [PATCH] Finer granularity for staging/reverting hunks.

---
 autoload/gitgutter.vim      | 20 ++++---------
 autoload/gitgutter/diff.vim | 60 ++++++++++++++++++++++++++++++-------
 autoload/gitgutter/hunk.vim | 13 ++++++++
 3 files changed, 69 insertions(+), 24 deletions(-)

diff --git a/autoload/gitgutter.vim b/autoload/gitgutter.vim
index a37a584..83413f6 100644
--- a/autoload/gitgutter.vim
+++ b/autoload/gitgutter.vim
@@ -19,7 +19,7 @@ function! gitgutter#process_buffer(bufnr, realtime)
     endif
     try
       if !a:realtime || gitgutter#utility#has_fresh_changes()
-        let diff = gitgutter#diff#run_diff(a:realtime || gitgutter#utility#has_unsaved_changes(), 1, 0)
+        let diff = gitgutter#diff#run_diff(a:realtime || gitgutter#utility#has_unsaved_changes(), 1)
         call gitgutter#hunk#set_hunks(gitgutter#diff#parse_diff(diff))
         let modified_lines = gitgutter#diff#process_hunks(gitgutter#hunk#hunks())
 
@@ -156,11 +156,8 @@ function! gitgutter#stage_hunk()
     " It doesn't make sense to stage a hunk otherwise.
     silent write
 
-    " construct a diff
-    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk(1, 1)
-
-    " apply the diff
-    call gitgutter#utility#system(gitgutter#utility#command_in_directory_of_file('git apply --cached --recount --allow-overlap - '), diff_for_hunk)
+    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk('stage')
+    call gitgutter#utility#system(gitgutter#utility#command_in_directory_of_file('git apply --cached --unidiff-zero - '), diff_for_hunk)
 
     " refresh gitgutter's view of buffer
     silent execute "GitGutter"
@@ -175,11 +172,8 @@ function! gitgutter#revert_hunk()
     " It doesn't make sense to stage a hunk otherwise.
     silent write
 
-    " construct a diff
-    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk(1, 1)
-
-    " apply the diff
-    call gitgutter#utility#system(gitgutter#utility#command_in_directory_of_file('git apply --reverse - '), diff_for_hunk)
+    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk('revert')
+    call gitgutter#utility#system(gitgutter#utility#command_in_directory_of_file('git apply --reverse --unidiff-zero - '), diff_for_hunk)
 
     " reload file
     silent edit
@@ -192,10 +186,8 @@ function! gitgutter#preview_hunk()
   if gitgutter#utility#is_active()
     silent write
 
-    " construct a diff
-    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk(0, 0)
+    let diff_for_hunk = gitgutter#diff#generate_diff_for_hunk('preview')
 
-    " preview the diff
     silent! wincmd P
     if !&previewwindow
       execute 'bo ' . &previewheight . ' new'
diff --git a/autoload/gitgutter/diff.vim b/autoload/gitgutter/diff.vim
index 2524c20..01b447b 100644
--- a/autoload/gitgutter/diff.vim
+++ b/autoload/gitgutter/diff.vim
@@ -10,7 +10,7 @@ endif
 let s:hunk_re = '^@@ -\(\d\+\),\?\(\d*\) +\(\d\+\),\?\(\d*\) @@'
 
 
-function! gitgutter#diff#run_diff(realtime, use_external_grep, lines_of_context)
+function! gitgutter#diff#run_diff(realtime, use_external_grep)
   " Wrap compound commands in parentheses to make Windows happy.
   let cmd = '('
 
@@ -33,7 +33,7 @@ function! gitgutter#diff#run_diff(realtime, use_external_grep, lines_of_context)
     execute 'silent write' buff_file
   endif
 
-  let cmd .= 'git diff --no-ext-diff --no-color -U'.a:lines_of_context.' '.g:gitgutter_diff_args.' -- '
+  let cmd .= 'git diff --no-ext-diff --no-color -U0 '.g:gitgutter_diff_args.' -- '
   if a:realtime
     let cmd .= blob_file.' '.buff_file
   else
@@ -214,17 +214,26 @@ function! gitgutter#diff#process_modified_and_removed(modifications, from_count,
   let a:modifications[-1] = [a:to_line + offset - 1, 'modified_removed']
 endfunction
 
-function! gitgutter#diff#generate_diff_for_hunk(keep_header, lines_of_context)
-  let diff = gitgutter#diff#run_diff(0, 0, a:lines_of_context)
-  let diff_for_hunk = gitgutter#diff#discard_hunks(diff, a:keep_header)
-  if !a:keep_header
-    " Discard summary line
-    let diff_for_hunk = join(split(diff_for_hunk, '\n')[1:-1], "\n")
+" Generates a zero-context diff for the current hunk.
+"
+" type - stage | revert | preview
+function! gitgutter#diff#generate_diff_for_hunk(type)
+  " Although (we assume) diff is up to date, we don't store it anywhere so we
+  " have to regenerate it now...
+  let diff = gitgutter#diff#run_diff(0, 0)
+  let diff_for_hunk = gitgutter#diff#discard_hunks(diff, a:type == 'stage' || a:type == 'revert')
+
+  if a:type == 'stage' || a:type == 'revert'
+    let diff_for_hunk = gitgutter#diff#adjust_hunk_summary(diff_for_hunk, a:type == 'stage')
   endif
+
   return diff_for_hunk
 endfunction
 
-" diff - with non-zero lines of context
+" Returns the diff with all hunks discarded except the current.
+"
+" diff        - the diff to process
+" keep_header - truthy to keep the diff header and hunk summary, falsy to discard it
 function! gitgutter#diff#discard_hunks(diff, keep_header)
   let modified_diff = []
   let keep_line = a:keep_header
@@ -237,5 +246,36 @@ function! gitgutter#diff#discard_hunks(diff, keep_header)
       call add(modified_diff, line)
     endif
   endfor
-  return join(modified_diff, "\n") . "\n"
+
+  if a:keep_header
+    return join(modified_diff, "\n") . "\n"
+  else
+    " Discard hunk summary too.
+    return join(modified_diff[1:], "\n") . "\n"
+  endif
 endfunction
+
+" Adjust hunk summary (from's / to's line number) to ignore changes above/before this one.
+"
+" diff_for_hunk - a diff containing only the hunk of interest
+" staging       - truthy if the hunk is to be staged, falsy if it is to be reverted
+"
+" TODO: push this down to #discard_hunks?
+function! gitgutter#diff#adjust_hunk_summary(diff_for_hunk, staging)
+  let line_adjustment = gitgutter#hunk#line_adjustment_for_current_hunk()
+  let adj_diff = []
+  for line in split(a:diff_for_hunk, '\n')
+    if match(line, s:hunk_re) != -1
+      if a:staging
+        " increment 'to' line number
+        let line = substitute(line, '+\@<=\(\d\+\)', '\=submatch(1)+line_adjustment', '')
+      else
+        " decrement 'from' line number
+        let line = substitute(line, '-\@<=\(\d\+\)', '\=submatch(1)-line_adjustment', '')
+      endif
+    endif
+    call add(adj_diff, line)
+  endfor
+  return join(adj_diff, "\n") . "\n"
+endfunction
+
diff --git a/autoload/gitgutter/hunk.vim b/autoload/gitgutter/hunk.vim
index 94a05ac..e50516e 100644
--- a/autoload/gitgutter/hunk.vim
+++ b/autoload/gitgutter/hunk.vim
@@ -94,3 +94,16 @@ function! gitgutter#hunk#cursor_in_hunk(hunk)
   return 0
 endfunction
 
+" Returns the number of lines the current hunk is offset from where it would
+" be if any changes above it in the file didn't exist.
+function! gitgutter#hunk#line_adjustment_for_current_hunk()
+  let adj = 0
+  for hunk in s:hunks
+    if gitgutter#hunk#cursor_in_hunk(hunk)
+      break
+    else
+      let adj += hunk[1] - hunk[3]
+    endif
+  endfor
+  return adj
+endfunction