Highlight line for specific commit in git log graph - regex

Question

I am trying to highlight the whole line for a specific commit in my git log graph. I have since before created a git log alias to format the output of my logs. I have attempted to highlight a specific line containing the commit-id, using my alias.
Alias in ~/.gitconfig
# Base command for log formatting
lg-base = "log --graph --decorate=short --decorate-refs-exclude='refs/tags/*' --color=always"
# Version 1 log format
lg1 = !"git lg-base --format=format:'%C(#f0890c)%h%C(reset) - %C(bold green)(%ar)%C(reset) %C(white)%s%C(reset) %C(dim white)- %an%C(reset)%C(#d10000)%d%C(reset)'"
Doing a test with searching for 6 months just because it should behave the same and might showcase my issue a bit better.
git lg1 | grep --color=always -E '(6 months).*|$'
Matches the correct lines. But it doesn't highlight the whole line to the right and when trying to highlight the left part of the line as well, it doesn't work as expected. Probably because of my lack in skills of using regex.
git lg1 | grep --color=always -E '.*(6 months).*|$'
Instead it marks the * in the beginning.
If you have a total other approach, that is fine with me as long as I can use my formatted git log alias.

Answer 1

Thomas' comment is the key to the issue here: although grep is adding its own color (or colour) changing escape sequences to highlight the line, Git has already put in color changing directives. Each such directive, for one of the named colors, looks like this:
ESC[numberm
where the number part is 30 through 37 for a foreground color and 40 through 47 for a background color (plus some extra codes for bold or dim, which I won't include here). (%C(reset) sends ESC [ m and your orange selector uses a 24-bit color directive, which is less widely supported than the eight base colors, which go back to the 1990s). Hence the original output reads:
* <sp> <orange> <hash-ID> <reset> <sp> - <sp> <blue> (n months ago) <reset> ...
The grep adds red, which is ESC [ 31 m, and a reset, around the matched expression—but the existing escapes within the expression remain.
The easiest way by far to avoid all this is to stop using color escape sequences at all, so that grep's added ones stick out like a sore red thumb. Of course that defeats your goal, which is to keep the color-changing escapes in lines that aren't highlighted. But you haven't explained what you'd like done with the color-changing escapes in lines, or parts of lines, that are highlighted. Answering that will determine what to do next.
There are any number of ways you could handle this. For instance, instead of %C(color)%<directive>%C(reset) you could use %x1b(name-of-color)%<directive>%x1b(reset) to insert the literal sequences ESC ( name of color or reset ), or assume that the terminal in question will use ANSI style escapes that end with the lowercase m character, and try to write something up in sed or awk (I'd use awk for something this complex, just because it's less like writing line noise) that does the match—awk supports regex matching—and if found, strips out the color sequences from the matched part and adds its own. Post-process this with something that inserts the appropriate terminal-dependent color-change sequences, or keep the original ESC [ ... m sequences on the assumption that you're in a window that uses that form, and you'll have the output you want (which you can now pipe through less -R if desired).
A skeleton awk program that does what you want is:
/<desired regex>/ { handle matched line; next; }
{ print }
The hard part is the "handle matched line". GNU awk has RSTART and RLENGTH to help out a lot; see, e.g., this answer. The substring of the line from the beginning to RSTART-1 wasn't matched (this may be empty), and the substring from RSTART+RLENGTH to the end of the line (which may also be empty) also was not matched; the substring of $0 at RSTART for length RLENGTH was matched and here's where you would strip out any color-changing sequences, if you want your basic red (or whatever) applied throughout.
Sample script (by Robin Hellmers)
Creating a script and placing it where you please, e.g.
~/.local/bin/highlight-commit.awk
with the contents
#!/usr/bin/nawk -f
BEGIN {
n = split(commits,arrayCommits," ");
background="145;0;0"
foreground="255;255;255"
}
{
# Compare with every given input e.g. commit id
for (i=1; i <= n; i++) {
if(match($0,arrayCommits[i])) {
# Remove any ANSI color escape sequence for matching row
gsub("\x1b\\[[0-9;]*m","",$0)
# Create ANSI color escape sequence for whole row
$0 = sprintf("\x1b[48;2;%sm\x1b[38;2;%sm%s\x1b[0m\x1b[0m",
background,
foreground,
$0);
break;
}
}
printf("%s\n", $0);
}
In ~/.gitconfig, add the following alias:
[alias]
highlight-commit = "!f() { git lg | awk -v commits=\"$*\" -f ~/.local/bin/highlight-commit.awk | less -XR; }; f"
By calling with e.g. two commits:
git highlight-commit 82451f8 310fca4