feat(git): replace vim-gitgutter with gitsigns.nvim

Swap the diff-sign plugin for gitsigns.

Point lualine's diff component at gitsigns' status dict instead of
letting it spawn its own git diff.

3 files changed, 77 insertions, 1 deletions

diff --git a/plugin/00-plugin.lua b/plugin/00-plugin.lua
index ac34066..6812ced 100644
--- a/plugin/00-plugin.lua
+++ b/plugin/00-plugin.lua
@@ -5,9 +5,9 @@ require() them.
 ]]
 
 vim.pack.add({
-	"https://github.com/airblade/vim-gitgutter",
 	"https://github.com/ibhagwan/fzf-lua",
 	"https://github.com/jbyuki/one-small-step-for-vimkind",
+	"https://github.com/lewis6991/gitsigns.nvim",
 	"https://github.com/maxmx03/solarized.nvim",
 	"https://github.com/MeanderingProgrammer/render-markdown.nvim",
 	"https://github.com/mfussenegger/nvim-dap",
diff --git a/plugin/50-color.lua b/plugin/50-color.lua
index f95711c..4cdbad0 100644
--- a/plugin/50-color.lua
+++ b/plugin/50-color.lua
@@ -100,7 +100,16 @@ local function bold_diff_diag()
 	end
 end
 
+-- Diff counts for lualine's diff component, sourced from gitsigns' status dict.
+local function gitsigns_diff()
+	local gs = vim.b.gitsigns_status_dict
+	if gs then
+		return { added = gs.added, modified = gs.changed, removed = gs.removed }
+	end
+end
+
 local lualine_sections = {
+	lualine_b = { "branch", { "diff", source = gitsigns_diff }, "diagnostics" },
 	lualine_c = { statuses },
 	lualine_x = { "encoding", "fileformat", "filetype", "lsp_status" },
 }
diff --git a/plugin/50-gitsigns.lua b/plugin/50-gitsigns.lua
new file mode 100644
index 0000000..88337b8
--- /dev/null
+++ b/plugin/50-gitsigns.lua
@@ -0,0 +1,67 @@
+--[[ 50-gitsigns.lua — git diff signs plus hunk navigation/staging, via gitsigns.nvim.
+
+Signs render by default in the always-on sign column; changed lines, their line numbers,
+and the changed words within them are highlighted too (linehl/numhl/word_diff).
+
+Keymaps are buffer-local (set in on_attach):
+`]c`/`[c` navigate hunks (falling through to Vim's builtin diff-mode nav when 'diff' is set)
+`<Leader>h…` stage/reset/preview/blame, and `ih` is a hunk text object.
+
+lualine reads the diff counts from gitsigns (see 50-color.lua).
+]]
+
+local gitsigns = require("gitsigns")
+
+-- Jump to the next/prev hunk, falling through to builtin ]c/[c when in diff mode.
+local function nav_hunk(direction)
+	if vim.wo.diff then
+		vim.cmd.normal({ direction == "next" and "]c" or "[c", bang = true })
+	else
+		gitsigns.nav_hunk(direction)
+	end
+end
+
+-- Stage/reset the visually-selected range of lines.
+local function stage_selection()
+	gitsigns.stage_hunk({ vim.fn.line("."), vim.fn.line("v") })
+end
+local function reset_selection()
+	gitsigns.reset_hunk({ vim.fn.line("."), vim.fn.line("v") })
+end
+
+local function blame_line()
+	gitsigns.blame_line({ full = true })
+end
+
+-- Buffer-local gitsigns keymaps; passed as `on_attach`.
+local function set_keymaps(bufnr)
+	local function map(mode, lhs, rhs, desc)
+		vim.keymap.set(mode, lhs, rhs, { buffer = bufnr, desc = desc })
+	end
+
+	-- Hunk navigation.
+	map("n", "]c", function()
+		nav_hunk("next")
+	end, "Next git hunk")
+	map("n", "[c", function()
+		nav_hunk("prev")
+	end, "Previous git hunk")
+
+	-- Staging / resetting. `stage_hunk` toggles, so it also unstages a staged hunk.
+	map("n", "<Leader>hs", gitsigns.stage_hunk, "Stage/unstage hunk")
+	map("n", "<Leader>hr", gitsigns.reset_hunk, "Reset hunk")
+	map("x", "<Leader>hs", stage_selection, "Stage selected hunk")
+	map("x", "<Leader>hr", reset_selection, "Reset selected hunk")
+	map("n", "<Leader>hS", gitsigns.stage_buffer, "Stage buffer")
+	map("n", "<Leader>hR", gitsigns.reset_buffer, "Reset buffer")
+
+	-- Inspecting.
+	map("n", "<Leader>hp", gitsigns.preview_hunk, "Preview hunk")
+	map("n", "<Leader>hb", blame_line, "Blame line")
+	map("n", "<Leader>hd", gitsigns.diffthis, "Diff against index")
+
+	-- Hunk text object.
+	map({ "o", "x" }, "ih", gitsigns.select_hunk, "Inner git hunk")
+end
+
+gitsigns.setup({ on_attach = set_keymaps, linehl = true, numhl = true, word_diff = true })