I am trying to get the git diff between 2 strings. The following command works:
git diff $(echo "my first string" | git hash-object -w --stdin) $(echo "my second string" | git hash-object -w --stdin) --word-diff
However, it fails if not executed inside a Git directory.
I believe this portion of the command is failing:
echo "my first string" | git hash-object -w --stdin
Is there any way around this so that it can be executed outside a Git directory?
I believe this portion of the command is failing:
echo "my first string" | git hash-object -w --stdinIs there any way around this so that it can be executed outside a git directory?
The problem you are having is because of the -w option that you pass to the git hash-object command. That option requires an existing repository as it has a side effect of writing the object into the git database.
Proof:
$ echo "my first string" | git hash-object -w --stdin
fatal: Not a git repository (or any parent up to mount point /home)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
$ echo "my first string" | git hash-object --stdin
3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165
However, since your final goal is to obtain the git diff between two given strings you have to have a git repository if you want to do it with the help of git hash-object1. To this end you can generate a temporary empty repository:
$ tmpgitrepo="$(mktemp -d)"
$ git init "$tmpgitrepo"
Initialized empty Git repository in /tmp/tmp.MqBqDI1ytM/.git/
$ (export GIT_DIR="$tmpgitrepo"/.git; git diff $(echo "my first string" | git hash-object -w --stdin) $(echo "my second string" | git hash-object -w --stdin) --word-diff)
diff --git a/3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165 b/2ab8560d75d92363c8cb128fb70b615129c63371
index 3616fde..2ab8560 100644
--- a/3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165
+++ b/2ab8560d75d92363c8cb128fb70b615129c63371
@@ -1 +1 @@
my [-first-]{+second+} string
$ rm -rf "$tmpgitrepo"
This approach can be packaged into a bash function:
git-diff-strings()
(
local tmpgitrepo="$(mktemp -d)"
trap "rm -rf $tmpgitrepo" EXIT
git init "$tmpgitrepo" &> /dev/null
export GIT_DIR="$tmpgitrepo"/.git
local s1="$1"
local s2="$2"
shift 2
git diff $(git hash-object -w --stdin <<< "$s1") $(git hash-object -w --stdin <<< "$s2") "$@"
)
Usage:
git-diff-strings <string1> <string2> [git-diff-options]
Example:
git-diff-strings "first string" "second string" --word-diff
1 Note that you can git diff two strings by creating 2 temporary files containing those strings, in which case you don't need a git repository.
@danday74 I am unable to write a comment based on your feedback (due to permissions on StackOverflow) so here is my answer. You can set the environment variable using GIT_DIR. If you do this on the multiple machines (you would need to be able to set this variable on such machines), then you will be able to reliably set --git-dir.
Hope this helps.
