Repository: dathere/qsv (language: rust)

Issue:
`qsv diff` documentation misstates effect of `--key`
If you have a Usage question, an Idea for a new feature; or a qsv story you want to share, go to [Discussions](https://github.com/jqnatividad/qsv/discussions).   
GitHub Issues is primarily used for bug reports, and for tracking Ideas that have been added to the [Backlog](https://github.com/jqnatividad/qsv/projects/1) for implementation.
---
**Describe the bug**
A clear and concise description of what the bug is.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to https://github.com/jqnatividad/qsv/blob/master/src/cmd/diff.rs#L25
2. Text says `qsv diff --key 0,1` will "Find the difference between two CSVs, but only for the first two columns"

**Expected behavior**
Documentation should say "Find the difference between two CSVs, comparing records that have the same values in the first two columns"

i.e., the `--key` flag does not identify the columns to be compared; it identifies the columns to be used to align records between the two files before comparing the other columns.

**Desktop (please complete the following information):**
 - OS: any
 - qsv Version: any


`qsv diff` documentation misstates effect of `--key`
If you have a Usage question, an Idea for a new feature; or a qsv story you want to share, go to [Discussions](https://github.com/jqnatividad/qsv/discussions).   
GitHub Issues is primarily used for bug reports, and for tracking Ideas that have been added to the [Backlog](https://github.com/jqnatividad/qsv/projects/1) for implementation.
---
**Describe the bug**
A clear and concise description of what the bug is.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to https://github.com/jqnatividad/qsv/blob/master/src/cmd/diff.rs#L25
2. Text says `qsv diff --key 0,1` will "Find the difference between two CSVs, but only for the first two columns"

**Expected behavior**
Documentation should say "Find the difference between two CSVs, comparing records that have the same values in the first two columns"

i.e., the `--key` flag does not identify the columns to be compared; it identifies the columns to be used to align records between the two files before comparing the other columns.

**Desktop (please complete the following information):**
 - OS: any
 - qsv Version: any




Discussion / hints:

Fix patch:
diff --git a/src/cmd/diff.rs b/src/cmd/diff.rs
index 6dc493e45..20c535d9d 100644
--- a/src/cmd/diff.rs
+++ b/src/cmd/diff.rs
@@ -22,11 +22,12 @@ and is written to a file:
     # or ';' as the delimiter
     qsv diff -o diff-semicolon.csv --delimiter-output ';' left.csv right.csv
 
-Find the difference between two CSVs, but only for the first two columns:
+Find the difference between two CSVs, comparing records that have the same values
+in the first two columns:
     qsv diff --key 0,1 left.csv right.csv
 
-Find the difference between two CSVs, but only for the first two columns and
-sort the result by the first and second column:
+Find the difference between two CSVs, comparing records that have the same values
+in the first two columns and sort the result by the first two columns:
     qsv diff -k 0,1 --sort-columns 0,1 left.csv right.csv
 
 Find the difference between two CSVs, but do not output headers in the result:


Test patch: