Hide Cargo.lock in git Diff

Whenever you add or update dependencies in Cargo.toml, the diff output in Cargo.lock can be verbose and distracting when I'm looking at git diff output:

$ git diff --stat
 Cargo.lock | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml |  3 +++
 2 files changed, 57 insertions(+)

$ git diff
diff --git a/Cargo.lock b/Cargo.lock
index c287579..a41401e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -151,6 +151,7 @@ dependencies = [
  "jsonrpsee",
  "log",
  "net2",
+ "pcap-file",
  "prettytable-rs",
  "serde",
  "serde_json",
@@ -344,6 +345,16 @@ dependencies = [
  "memchr",
 ]

+[[package]]
+ ... pages of [[package]] updates

Hiding via Git CLI

You can temporarily hide the Cargo.lock diff output by adding a path filter to the git diff command:

$ git diff ':!*lock'
diff --git a/Cargo.toml b/Cargo.toml
index a3cd170..3d68210 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,3 +41,6 @@ tokio = {version = "^0.2.11", features=["macros", "tcp", "time", "stream"]}
 tokio-util = { version = "^0.2", features=["codec"]}
 toml = "0.5"
 twoway = "0.2.0"
+
+[dev-dependencies]
+pcap-file = "*"

You can also add this as an alias in your Git configuration for quick recall:

~/.gitconfig

...
[alias]
    diff-no-lock = "!git diff ':!*lock'"

Hiding via a Custom Hunk Header

For a more permanent per-project or global fix, you can add special handling for *.lock (or any file you want) when using git diff by adding a hunk header to customize the output.

Add a Hunk Header

Since our goal is to not show any output for Cargo.lock files, our hunk header command will be /bin/true (or /usr/bin/true for MacOS):

~/.gitconfig

...
[diff "hidden"]
     command = /bin/true

Target .lock Files in Git Attributes

Now we need to associate .lock files to use our custom hunk header. Create or edit your .gitattributes file:

~/.gitattributes

*.lock  diff=hidden

If you don't already have a .gitattributes file, you will also need to point your Git config at this new file:

~/.gitconfig

...
[core]
    attributesfile = ~/.gitattributes

Success!

Now enjoy your Cargo.update free diff output:

$ git diff --stat
 Cargo.lock | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml |  3 +++
 2 files changed, 57 insertions(+)
$ git diff
diff --git a/Cargo.toml b/Cargo.toml
index a3cd170..3d68210 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,3 +41,6 @@ tokio = {version = "^0.2.11", features=["macros", "tcp", "time", "stream"]}
 tokio-util = { version = "^0.2", features=["codec"]}
 toml = "0.5"
 twoway = "0.2.0"
+
+[dev-dependencies]
+pcap-file = "*"

Caveat

Adding a hunk header will affect Git patches (E.g. git diff > ~/mychange.patch) since it will not include any of the Cargo.lock changes. If you send someone a patch, that person can run cargo update to re-build the Cargo.lock file, or you can temporarily disable the hunk header in your .gitconfig.