GitHub doesn't show rich diffs for Rmd files. That can make collaborative writing tough. Here's how to see rich diffs of two commits of a single R Markdown document on a GitHub repo or local Git repo

inspect-rmd-diff-from-last-commit.R

# another method
# remotes::install_github("ropenscilabs/reviewer")
browseURL(reviewer::diff_rmd("analysis/paper/paper.qmd", 
                             # this gets the sha of the previous commit
                             git2r::commits(n=2)[[2]]$sha)$raw)

rich-diffs-rmd-in-local-git-repo.R

# How to see rich diffs of two commits of a single R Markdown document in a local Git repo

# https://github.com/lorenzwalthert/gitsum
library("gitsum")
library("tidyverse")

# To browse the commits locally, open an RStudio 
# project that is using Git version control, then ...

# Set the path within the project to the Rmd file 
# in the project that we want to compare versions of
file_path <- "analysis/paper/paper.Rmd"

# Make a data frame that stores the git commit history, 
# one row per commit
init_gitsum()
tbl_out <- parse_log_detailed() %>%
  select(date, author_name, message, hash)

# View this dataframe to pick the specific commits to compare
View(tbl_out)

# choose two commits to compare, here I've got the most recent 
# one (the last row of the table), and the one immediately before that 
i <- nrow(tbl_out) 
j <- nrow(tbl_out) - 2

# consrtruct the terminal commants using the SHA of the commits we want to 
# compare, and the file path
git_show_str_1 <- str_glue('git show ', tbl_out[i, ]$hash, ":", file_path)
git_show_str_2 <- str_glue('git show ', tbl_out[j, ]$hash, ":", file_path)

# get the contents of the file at each commit and 
# store in a vector
earlier_commit <- system(git_show_str_2, intern = TRUE)
later_commit <- system(git_show_str_1, intern = TRUE)

# compute differences and visualise
diffobj::diffChr(earlier_commit, 
                  later_commit, 
                  mode = "sidebyside")

# another option: https://ropenscilabs.github.io/reviewer/articles/reviewer.html

rich-diffs-rmd-on-github.R

# How to see rich diffs of two commits of a single R Markdown document on a GitHub repo (on the master branch only)

# Edit this to use the repo that has the file you want to inspect
gh_account_and_repo <- "LiYingWang/kwl.pottery"

# Edit this to use the single file that you want to inspect
# start the path here from the top level of the github repo
gh_file_path <- "analysis/paper/paper.Rmd"

# Run this next line to open a web page to see the commit history 
# of this file so we can copy the SHA ids to use in the next step. 
# Look for the little clipboard icon to click on to copy the full SHA, 
# and past the SHAs in the next step below
browseURL(file.path(
  "https://github.com",
  gh_account_and_repo,
  "commits/master",
  gh_file_path
))

# Edit these to get the full SHA for the commits you want to compare, get
# the full SHA from the GitHub webpage that was opened in the previous step
commit_1_sha <- "8249ffc832acfb4839dfb9e5f838d45b82ca0063" # a recent commit
commit_2_sha <- "a05cad1b678a31c9def1860cbceeba4cbfb98577" # an earlier commit

# Don't change this
gh_raw <- "https://raw.githubusercontent.com"

# run these lines...
later_commit <- file.path(gh_raw, gh_account_and_repo, commit_1_sha, gh_file_path)
earlier_commit <- file.path(gh_raw, gh_account_and_repo, commit_2_sha, gh_file_path)

# run these lines to view the rich diff:
diffobj::diffFile(earlier_commit, 
         later_commit, 
         mode = "sidebyside")

Here's an example of the output from this process, it pops up in the RStudio viewer, and can be popped out into a browser tab: