Fix first commit in preview

Author: aaronhallaert

lua/advanced_git_search/git_utils.lua

@@ -188,44 +188,84 @@ M.git_log_grepper_on_file = function(bufnr)
     end, git_log_entry_maker)
 end
 
+local previous_commit_hash = function(commit_hash)
+    local command = "git rev-parse " .. commit_hash .. "~"
+    local handle = io.popen(command)
+    local output = handle:read("*a")
+    handle:close()
+
+    output = string.gsub(output, "\n", "")
+    return output
+end
+
+--- Determine the historic file name for a given commit hash and buffer number
+--- @param commit_hash string
+--- @param bufnr number
+--- @return string | nil file_path historic file name relative to git root
 local determine_historic_file_name = function(commit_hash, bufnr)
-    local current_file_name = file.relative_path(bufnr)
+    local current_file_name = file.git_relative_path(bufnr)
 
-    local command = "git log -M --diff-filter=R --follow --name-status --summary "
+    local command = "cd "
+        .. file.git_dir()
+        .. " && "
+        .. "git --no-pager log -M --follow --name-status --oneline "
         .. commit_hash
-        .. ".. -- "
+        .. "~.. -- "
         .. current_file_name
-        .. " | grep ^R | tail -1 | cut -f2,2"
+        .. " | tail -2"
 
     local handle = io.popen(command)
     local output = handle:read("*a")
     handle:close()
 
-    output = string.gsub(output, "\n", "")
-    if output == "" then
-        output = file.git_relative_path(bufnr)
+    -- first line contains the commit_hash and message
+    -- second line contains the file status and file name (when rename, 2 filenames are present)
+    output = utils.split_string(output, "\n")
+
+    if output[1] == nil or output[2] == nil then
+        return nil
     end
 
-    -- output is relative to git root
-    return output
+    local returned_hash = utils.split_string(output[1])[1]
+
+    -- only return the file name if the commit hash matches, otherwise return nil
+    if string.sub(returned_hash, 1, 7) == string.sub(commit_hash, 1, 7) then
+        local split_output = utils.split_string(output[2])
+        return split_output[#split_output]
+    else
+        return nil
+    end
 end
 
 M.git_diff_previewer_file = function(bufnr)
     return previewers.new_termopen_previewer({
         get_command = function(entry)
             local commit_hash = entry.opts.commit_hash
 
-            local prev_commit = string.format("%s~", commit_hash)
-            return git_diff_command({
-                "git",
-                "diff",
-                prev_commit
-                    .. ":"
-                    .. determine_historic_file_name(prev_commit, bufnr),
-                commit_hash
-                    .. ":"
-                    .. determine_historic_file_name(commit_hash, bufnr),
-            })
+            local prev_commit = previous_commit_hash(commit_hash)
+            if determine_historic_file_name(prev_commit, bufnr) == nil then
+                return git_diff_command({
+                    "git",
+                    "diff",
+                    prev_commit,
+                    commit_hash,
+                    "--",
+                    file.git_dir()
+                        .. "/"
+                        .. determine_historic_file_name(commit_hash, bufnr),
+                })
+            else
+                return git_diff_command({
+                    "git",
+                    "diff",
+                    prev_commit
+                        .. ":"
+                        .. determine_historic_file_name(prev_commit, bufnr),
+                    commit_hash
+                        .. ":"
+                        .. determine_historic_file_name(commit_hash, bufnr),
+                })
+            end
         end,
     })
 end

lua/advanced_git_search/utils/file.lua

@@ -8,6 +8,10 @@ M.relative_path = function(bufnr)
     return vim.fn.expand("#" .. bufnr .. ":~:.")
 end
 
+M.git_dir = function()
+    return M.find_first_ancestor_dir_or_file(vim.fn.getcwd(), ".git")
+end
+
 M.file_name = function(bufnr)
     return vim.fn.expand("#" .. bufnr .. ":t")
 end