How can a patchfile created with `git-log -p <filename>` be applied to create all the commits included?

Question

Background: this question. git apply <patchfile> just recreates the file but without committing the history, which in this case would be desireable. Is there any switch for git-apply to do so? Or is there a way to convert the patchfile into a git-am compatible file? (Currently, git-am complains "Patch format detection failed")

Answer 1

You asked, so here it is.

I used this script, but it's all rather fragile. Treat it an as inspiration, not as a reasonable solution.

It extracts (date / author / commit message / patch) from output of git log -p, and then runs patch+git add+git apply for all, in reverse order.

There's probably some way of automatically figuring out correct patch_level, but I didn't bother. And pass author to git apply if it's not all you.

#!/usr/bin/env ruby

class String
  def shell_escape
    if empty?
      "''"
    elsif %r{\A[0-9A-Za-z+,./:=@_-]+\z} =~ self
      self
    else
      result = ''
      scan(/('+)|[^']+/) {
        if $1
          result << %q{\'} * $1.length
        else
          result << "'#{$&}'"
        end
      }
      result
    end
  end
end

dir1, dir2, *files = ARGV

patchlog = Dir.chdir(dir1){`git log -p #{files.map(&:shell_escape).join(" ")}`}

patches = []
patchlog.each_line{|line|
  if line =~ /\Acommit/
    patches << {}
  elsif line =~ /\A(Author|Date):\s*(.*)/
    patches[-1][$1] = $2
  elsif patches[-1][:diff].nil? and line !~ /\Adiff/
    (patches[-1][:msg] ||= "") << line
  else
    (patches[-1][:diff] ||= "") << line
  end
}

patch_level = 2
skip = 0
dry_run = false

patches.reverse[skip..-1].each{|patch|
  author = patch["Author"].strip
  date = patch["Date"].strip
  msg = patch[:msg].strip
  diff = patch[:diff]

  if dry_run
    puts ["git", "commit", "-m", msg, "--date", date].join(" ")
    next
  end

  Dir.chdir(dir2){
    IO.popen("patch -p#{patch_level}", "w"){|fh|
      fh.puts diff
    }
    system "git", "add", *files
    system "git", "commit", "-m", msg, "--date", date
  }
}