将git commit消息的主题行限制为50个字符

Question

我经常vim用来格式化我的git提交消息.我越来越 受欢迎的趋势是提交消息的第一行应限制为50个字符,然后后续行应限制为72个字符.

我已经知道如何根据我的vimrc文件将我的提交换行设置为72个字符:

syntax on
au FileType gitcommit set tw=72

有没有办法让vim第一行自动换行50个字符,然后是72个字符？

一个同样好的答案可以突出显示第50行仅在第一行之后的所有内容,以表明我的标题太长了...

Answer 1

You can use the CursorMoved and CursorMovedI autocommands to set the desired textwidth (or any other setting) based on the line the cursor is currently on:

augroup gitsetup
        autocmd!

        " Only set these commands up for git commits
        autocmd FileType gitcommit
                \ autocmd CursorMoved,CursorMovedI *
                        \ let &l:textwidth = line('.') == 1 ? 50 : 72
augroup end

The basic logic is simple: let &l:textwidth = line('.') == 1 ? 50 : 72, although the nested autocommands make it look rather funky. You could extract some of it out to a script-local function (fun! s:setup_git()) and call that, if you prefer.

The &:l syntax is the same as setlocal, by the way (but with setlocal we can't use an expression such as on the right-hand-side, only a simple string).

Some related questions:

• Line number specific text-width setting.
• Set paste mode when at beginning of line but auto-indent mode when anywhere else on the line?

Note that the default gitcommit.vim syntax file already stops highlighting the first line after 50 characters. From /usr/share/vim/vim80/syntax/gitcommit.vim:

syn match   gitcommitSummary    "^.\{0,50\}" contained containedin=gitcommitFirstLine nextgroup=gitcommitOverflow contains=@Spell
[..]
hi def link gitcommitSummary        Keyword

Only the first 50 lines get highlighted as a "Keyword" (light brown in my colour scheme), after that no highlighting is applied.

If also has:

syn match   gitcommitOverflow   ".*" contained contains=@Spell
[..]
"hi def link gitcommitOverflow      Error

Notice how it's commented out, probably because it's a bit too opinionated. You can easily add this to your vimrc though:

augroup gitsetup
        autocmd!

        " Only set these commands up for git commits
        autocmd FileType gitcommit
                \  hi def link gitcommitOverflow Error
                \| autocmd CursorMoved,CursorMovedI *
                        \  let &l:textwidth = line('.') == 1 ? 50 : 72
augroup end

Which will make everything after 50 characters show up as an error (you could, if you want, also use less obtrusive colours by choosing a different highlight group).