Update README.md

README.md

@@ -11,7 +11,8 @@ Code churn has several definitions, the one that to me provides the most value a
 
 Solutions that I've found online looked at changes to files irrespective whether these are new changes or edits to existing lines of code (LOC) within existing files. Hence this solution that segments line-of-code edits (churn) with new code changes (contribution).
 
-*Tested with Python version 3.5.3 and Git version 2.20.1*
+*Tested with:
+* Python versions 3.5.3 and 3.8.8.Git version 2.20.1*
 
 # How it works
 This lightweight script looks at commits per author for a given date range on the **current branch**. For each commit it bookkeeps the files that were changed along with the LOC for each file. LOC are kept in a sparse structure and changes per LOC are taken into account as the program loops. When a change to the same LOC is detected it updates this separately to bookkeep the true code churn.
@@ -24,33 +25,46 @@ Positional (required) arguments:
 - **after**        after a certain date, in YYYY[-MM[-DD]] format
 - **before**     before a certain date, in YYYY[-MM[-DD]] format
 - **author**     author string (not a committer), leave blank to scope all authors
-- **dir**            include Git repository directory
+- **dir**            include Git repository directory (specified as an absolute path)
 
 Optional arguments:
 - **-h, --h, --help**    show this help message and exit
 - **-exdir**                   exclude Git repository subdirectory
+- **-start-commit**    search _from_ a certain commit, in short SHA format
+- **-end-commit**      search _to_ a certain commit, in short SHA format
 
-## Usage Example 1
+## Usage example with a specific author
 ```bash
 python ./gitcodechurn.py after="2018-11-29" before="2019-03-01" author="an author" dir="/Users/myname/myrepo" -exdir="excluded-directory"
 ```
-## Output 1
+### Output
 ```bash
 author:       an author
 contribution: 844
 churn:        -28
 ```
 
-## Usage Example 2
+## Usage example without specifying an author
 ```bash
 python ./gitcodechurn.py after="2018-11-29" before="2019-03-01" author="" dir="/Users/myname/myrepo" -exdir="excluded-directory"
 ```
-## Output 2
+### Output
 ```bash
 authors:      author1, author2, author3
 contribution: 4423
 churn:        -543
 ```
 
-Outputs of Usage Example 1 can be used as part of a pipeline that generates bar charts for reports:
+## Usage example without valid before and after dates, but instead between two commit hashes
+```bash
+python ./gitcodechurn.py after="" before="" -start-commit="6334225" -end-commit="9af2a6e" author="" dir="/Users/myname/myrepo" -exdir="excluded-directory"
+```
+### Output
+```bash
+authors:      author1, author2
+contribution: 467
+churn:        -48
+```
+
+Outputs can be used as part of a pipeline (not included) that generates bar charts for reports. For example:
 ![contribution vs churn example chart](/chart.png)