git diff-tree

What git show uses internally.

🎯 What & why

Diffs two tree-ish objects (or one tree against its parent) and is what git show and git log -p use under the hood. If you're scripting commit -> tree -> diff, this is the workhorse you actually call.

🧠 Mental model

Trees in, diff records out. With one tree it walks a commit's parents; with two it compares them directly; with -r it recurses into subdirectories instead of summarizing them as a single tree change.

🛠️ Synopsis

git diff-tree [--stdin] [-m] [-s] [-v] [--pretty] [-t] [-r] [--root]
              [<common-diff-options>] <tree-ish> [<tree-ish>] [<path>...]

🎚️ Switches & options

Flag	What it does
`<tree1> [<tree2>]`	One tree-ish diffs commit-vs-parent; two tree-ishes diffs them directly.
`-r / --recursive`	Recurse into subtrees; without it, directory changes collapse to a single entry.
`--root`	For root commits, show the full tree as an addition instead of producing nothing.
`-c`	For merges, show a combined diff against all parents (only paths changed vs every parent).
`--cc`	Like `-c` but further compresses uninteresting hunks; what `git show` uses for merges.
`--combined-all-paths`	With `-c/--cc`, list the path under every parent (useful for renames across a merge).
`-m`	For merges, emit a separate diff against each parent instead of a combined one.
`--name-only / --raw`	Trim output to paths only, or emit the machine-readable raw record format.

💡 Use cases

Scripts that walk rev-list output and want patches or raw records per commit.
Building changelog or release-note generators without invoking porcelain.
Feeding git diff-pairs with explicit (oid1, oid2) records via -z --raw.
Inspecting merge commits exactly the way git show does, for tooling parity.

🧪 Examples

Patch for the tip commit, recursive

git diff-tree -p -r HEAD

Raw, NUL-terminated records for downstream tools

git diff-tree -r -z --raw HEAD^ HEAD

Combined merge diff like git show does

git diff-tree --cc -r <merge-sha>

Just the names of files changed in a commit

git diff-tree --no-commit-id --name-only -r HEAD

🎓 Recommendations

Default to -r; without it directory-level changes collapse and you'll wonder where your files went.
For root commits in scripts, add --root so the very first commit isn't silently empty.
Match git show's behavior for merges with --cc; use -m only when you genuinely want per-parent diffs.

🪤 Common pitfalls

Without -r, a change inside src/foo/bar.c shows up only as src changing - confusing if you weren't expecting tree-level output.
By default the first line of output is the commit ID; pass --no-commit-id when piping raw records or it'll corrupt parsers.
On merges with no -c/--cc/-m, diff-tree shows nothing for the merge commit - that's intentional, not a bug.

🔗 Related modules

📝 Quiz

Hit each option, then Check answers. Score is recorded; Next is always open.